A NOAA satellite view of a massive Hurricane Erin churning off the U.S. East Coast taken August 20, 2025. (Image credit: NOAA Satellites)
Explainer: Understanding hurricane hazards
Storm surge
Inland flooding
Wind
Tornadoes
Hurricane Season is a frightening time for many, and understandably so — it produces some of the strongest storms on Earth every year, disrupting homes, businesses, tourism, governments, and daily lifestyles.
We are taking a deeper dive into the four main hazards threatening communities when a hurricane strikes: wind, tornadoes, inland flooding, and storm surge. Although they pose a threat to human life and property in different ways, all four can happen simultaneously when a hurricane strikes.
Before we get to the hazards, however, it's important to understand some background information in hurricane forecasting and preparedness. What are the first things meteorologists look for before a hurricane is named? What are the different warnings when a hurricane strikes, and what do they mean? How do I know when exactly the storm will arrive, and how bad will it be?
Look no further — here’s how we know what to expect when a hurricane is brewing:
Start with the Tropical Weather Outlook
Long before a hurricane ever develops, Hurricane Specialists at the National Hurricane Center in Miami, FL, are watching the tropics for signs of tropical disturbances. These could be tropical waves, stalled cold fronts, or even remnants from a previous hurricane — any low pressure system over warm water that could become stronger.
When weather models begin to show that a disturbance may strengthen, the forecasters take notice. They mark the region with a low, medium, or high chance of development. Development typically means it becomes a tropical depression, the weakest form of a tropical system.
Video file
These forecasts are called ‘Tropical Weather Outlooks’ (TWOs). This is the first graphic that appears when you visit hurricanes.gov because, with one glance, you get a summary of all significant tropical weather in the entire Western hemisphere.
Once a tropical depression or tropical storm has formed, an official forecast is released to show how the storm will progress. This is often referred to as the ‘Forecast Cone,’ and it shows where the center of the storm is likely to track and how strong the storm may get. For the latest forecast on each storm, you can always visit hurricanes.gov .
If a depression grows to tropical storm strength (see wind article for this classification), it officially receives a name. These names are pre-set each season and updated by the World Meteorological Organization.
When a hurricane nears landfall
Now it is time to put your hurricane preparedness plan into action. Stay connected to your trusted source of information, as the weather conditions can be unpredictable and things could change rapidly. Communicate to your loved ones what your plans are so others can look out for you after the event is over.
Long before a hurricane impacts land, it can bring dangerous rip currents to coastal areas. This can occur even if the beach weather is sunny and the hurricane is hundreds of miles offshore. The NHC has new graphics that analyze the nation’s rip current risk here.
In the days leading up to landfall, Hurricane Watches and Tropical Storm Watches will be issued, identifying the regions that are likely to experience wind impacts from the storm within 48 hours.
When landfall is imminent (within <36 hours), Hurricane Warnings are posted in the locations that will experience hurricane-force winds from the storm.
Sometimes, there is confusion about the forecast cone and landfall. As a hurricane nears, the forecast cone shrinks because forecasters have a much better idea of where the center of the storm will track. It is important to keep in mind that impacts from a hurricane extend far from the center of the storm.
Conclusion
Now that you have a better understanding of where to find information when a hurricane threatens, you’re ready to learn about the main hazards a hurricane brings when it makes landfall.
Not everyone is familiar with the term storm surge. It often gets caught up with simpler terms like ‘high surf’ and ‘extreme flooding’, but these don’t give it the proper distinction it deserves.
Storm surge is historically the deadliest part of hurricanes, accounting for 49% of deaths from 1963-2012 (Rappaport, NHC 2014 offsite link).
Storm surge forecasting, awareness, and preparedness has improved by leaps and bounds in the last ten years, helping to bring the average death toll down significantly. Truly understanding what storm surge is and how it happens is the first step to creating a nation that is more prepared to battle a hurricane’s most powerful hazard.
What is it?
Simply put, storm surge is the rise in sea level associated with a hurricane. This rise can be feet above what the normal sea level would be, meaning it overtakes sea walls, sand dunes, and even buildings, flooding areas that are normally dry.
As a hurricane nears the coastline, its strong winds push ocean water onshore for hours on end. This can push ocean water well inland, including up rivers and bays, submerging communities miles away from the coast. Just two feet of surge can lift a vehicle, six feet stands taller than most people, and ten feet can submerge the first floor of homes. Check out this VR simulation.
What makes surge worse
Hurricane intensity is just one factor that plays into the severity of storm surge. Stronger winds have the ability to push more water, but the size and speed of a hurricane also play an important role.
Larger hurricanes — that is, those with a larger diameter of strong winds — blow more water towards shore. This translates to a more extensive storm surge along the coast. Pair this with a slow hurricane (moving at less than 10 miles per hour), and the ocean water is battered along the coastline relentlessly for hours, making a surge that moves farther inland.
A comparison that perfectly demonstrates this is between Hurricane Ian in 2022 and Hurricane Charley in 2004. They made landfall at the same strength, time, and location across southwestern Florida. Their only differences were speed and size: Charley was a small, fast-moving storm while Ian was large and slow-moving. The result was a devastating storm surge caused by Ian that took dozens of lives, and a minor storm surge from Charley. For more on this case study, visit this NHC blog post offsite link.
Location relative to the hurricane matters as well. The worst place for storm surge is usually just to the right of the hurricane's eye. Here, the strongest winds push the most water onto shore with the most force.
Small wobbles in a hurricane’s track can change a storm surge forecast tremendously. In 2024, if Hurricane Milton had moved just 20 miles north, it would have brought a devastating storm surge into the Tampa metro. Instead, it stayed far enough south to keep the surge mild.
Ocean bathymetry, the ocean floor’s shape, matters a bit too. Islands are generally protected from the worst surge because they typically have steep ocean floor shelves surrounding them. On the other hand, areas like the U.S. Gulf Coast have a gradual ocean floor that slopes up to the coast, meaning water can move easier and impact land sooner.
NHC storm surge unit
With all of these variables at play, the National Hurricane Center in Miami, FL, has its own Storm Surge Unit to independently analyze these risks for the entire U.S. and beyond. For every storm, the team forecasts how states, counties, and communities will be affected based on all the factors above.
Historic examples
- Hurricane Ian in 2022 produced storm surge up to 15 feet above normally dry ground in Fort Myers Beach, FL, bringing devastation to many vacation & retirement communities in the area.
- Hurricane Laura in 2020 brought storm surge up to 18 feet above normally dry ground along the western Louisiana coastline.
- Hurricane Camille in 1969 brought 24 feet above normal tide levels of storm surge to the Mississippi coast.
- Hurricane Katrina in 2005 holds the record for the highest storm surge ever recorded in the U.S. — a staggering 25-28 feet above normal tide levels.
In the last ten years, storm surge has lost its distinction as the deadliest hazard associated with tropical cyclones. This is partly thanks to more forecast information and a better public understanding of the phenomenon. Nonetheless, it is imperative to heed evacuation orders in storm surge zones when a hurricane arrives and to continue supporting public awareness of the hazard.
Video file
Counter-clockwise rotation of a hurricane means that the left side of the eye often experiences winds that push water away from shore. In 2017, Hurricane Irma caused this exact phenomena over Tampa Bay, draining out much of the water.
Hurricanes bring with them a lot of rain — that’s no secret. But once the storm weakens and moves inland, this rain becomes the leading killer.
Inland flooding broadens a hurricane’s danger to the millions of people who don’t live along the coast. Hurricanes can weaken to their “death,” yet the trillions of gallons of rain they brought with them remain. Tropical storms that do not reach hurricane status can still be very dangerous, causing heavy rainfall that increases the risk of inland flooding and mudslides in steep terrain.
Here, we explore what inland flooding looks like and how you can be prepared.
The immediate rain
On average, tropical cyclones bring more than 6 inches of rain to thousands of square miles after hitting land. This can quickly cause flooded roadways, swollen rivers, and dangerous flash floods — or floods that form in a matter of minutes.
While water rescue teams are prepared for this, there are often too many rescues for them to do in such inclement weather. This leads to residents becoming trapped in homes until the weather improves or until the water goes down. This can take days or even weeks.
How it becomes catastrophic
Inland flooding is exacerbated by three main factors: urbanization, topography, and concurrent weather systems.
Highly urbanized areas often have a difficult time draining off water thanks to concrete, which causes runoff rather than drainage. If draining systems are not properly located, cleaned, or designed, they can quickly back up and cause flooding in densely populated areas.
Topography is perhaps the biggest amplifier of heavy rains. Mountainous terrain funnels all water into nearby streams and rivers, causing them to swell quickly. This also loosens mountain soil, making landslides more likely to occur.
Finally, other weather systems can combine with a tropical cyclone or its remnants, adding to the total rainfall or simply ‘stalling’ the storm system. This causes it to sit over the same areas, bringing heavy rain for days on end that quickly overwhelm all waterways and drainage systems.
Why strength is not necessarily an indicator of rainfall amounts
Tropical cyclones — regardless of their strength — have an ability to hold extremely large amounts of water. All tropical cyclones form over the ocean, where the atmosphere is primed for holding water until it can’t anymore. The cycle is never ending, and any tropical system that makes landfall pushes all of this moisture over land.
That is why the strength of a tropical depression, tropical storm, or hurricane at landfall is not the most important factor when it comes to rainfall potential.
‘PWAT’, or Precipitable Water, is a measurement describing how deep the water would be if all the water vapor in a column of air turned to rain. The average global PWAT offsite link is 0.85 inches (generally dry), while hurricanes can have PWAT values over 3 inches (extremely saturated).
Historic examples
The most recent example of deadly inland flooding came from Hurricane Helene in 2024. Before Helene made landfall, a cold front brought 4-6 inches of rain across the Appalachian Mountains of North Carolina. After Helene made landfall in Florida, it travelled northward into that very region, where it combined (or merged) with another area of low pressure associated with a prior system. This caused days of heavy rain on top of already-saturated soil, leading to a flooding catastrophe in the region. 107 fatalities occurred in the region alone.
In 2021, Hurricane Ida made a devastating Category 4 landfall in Louisiana. However, the worst of the flooding came in the Northeast. Up to ten inches of rain fell along the I-95 corridor, leading to historic flooding across the region. New York City saw dozens of apartment building basements flooded while residents struggled to escape. 43 people lost their lives across the Northeast even though it was only Ida’s remnants that moved through the area.
In 2017, Hurricane Harvey rewrote the record books. A Category 4 landfall was only the start of a nightmare for southeast Texas. Harvey ‘stalled’, or remained stationary, for over four days. Rain totals over 60 inches were recorded, flooding the Houston metro and all surrounding areas. The storm cost $160 billion, making it the 2nd costliest of all time, only behind Hurricane Katrina in 2005.
Even six inches of flood water can sweep an adult off their feet, and as little as one foot of water can float a vehicle.
When people think of a hurricane, the first hazard that comes to mind is the wind. Tropical cyclones are classified based on their maximum sustained winds, and hurricanes specifically are rated according to the Saffir-Simpson Wind Scale. The raw power of these winds pose a multitude of hazards to life and property.
Here, we’ll break down what different wind speeds mean and how they might affect your community.
Tropical depression
As an area of low pressure strengthens, so do its winds. When a tropical cyclone has sustained winds below 39 mph (34 knots), it is considered a tropical depression.
Tropical storm
When winds reach 39 mph (34 knots) or more, a depression is reclassified as a tropical storm. At this point, a name is given to the system. For a complete list of tropical storm & hurricane names each year, and a look at how these names are decided, visit the National Hurricane Center's Tropical Cyclone Names page.
When a tropical storm is confirmed to have sustained winds of 74 mph (64 knots) or greater, the system is reclassified as a hurricane.
The highest 1-minute average wind that is found in a tropical cyclone at a particular time. These are not wind gusts, but rather winds that are constantly blowing at/near a certain speed. It is the standard measure of a tropical cyclone's intensity in the Atlantic and Eastern/Central Pacific basin.
The saffir-simpson wind scale
The Saffir-Simpson Wind Scale is a rating system that ranges from 1 to 5 and is based solely on the maximum sustained wind speed of a hurricane. It is important to note that this scale considers only wind hazards and does not account for storm surge, rainfall flooding, or tornadoes. For more information about the Saffir-Simpson Wind Scale, please see this detailed description (PDF)
In strong winds, debris can quickly become projectiles and pose a danger to life and property. The winds can affect areas along the coast or far inland. In 2024, Hurricane Helene struck the Big Bend of Florida, causing extensive damage on the coast as well as inland across the southeastern states. Hurricane-force wind gusts brought down many trees across Georgia and the Carolinas — areas with dense tree canopies — causing extensive power outages and dozens of fatalities.
Products available from the National Hurricane Center
The National Hurricane Center provides wind probabilities that indicate the likelihood that winds will reach tropical storm force or hurricane force at specific locations along the storm's path. As the system approaches, these probabilities increase or decrease based on improved forecasts.
It is crucial to not underestimate the power of the winds associated with tropical systems. Recognizing that dangers extend far from the storm’s center is essential to preparedness and safety. As always, visit hurricanes.gov to see your wind forecast when a storm nears.
Tornadoes and hurricanes: different storms at the same time
Tornadoes are sometimes thought to be a problem of the high plains — most commonly, the infamous “Tornado Alley.” Yes, twisters are common here, but it is certainly not the only place they occur.
As a matter of fact, tornadoes often occur in hurricanes.
Hurricanes are nature’s finest display of power, made by a shield of convective counterclockwise rotation. The scale of this circulation is massive — spanning hundreds of miles across — and dwarfs the size of the average tornado, which is 50 yards across.
We speak about a tornado in a hurricane because the tornado forms under the umbrella of the hurricane’s broad rotation, not just near it. However, these tornadoes still originate from their own complex rotation and dynamics, independent of the hurricane’s. The hurricane just provides the perfect environment for tornadoes to occur.
It all starts when a hurricane comes close to land.
This dramatic shift from the warm ocean waters to Earth’s rocky terrain means that hurricanes encounter a completely different environment. The warm, moist air above the ocean surface is replaced by a turbulent and comparatively dry air above land. Winds that once blew freely over the sea encounter hills, mountains, buildings, and drag over land. The ocean is a hurricane's sole fuel source, and upon landfall, it is completely cut off.
This process causes the hurricane to experience wind shear. Wind shear is a change of wind speed and/or direction with height in the atmosphere. It is the death of hurricanes, causing their vertically-stacked eyewall to become tilted and off balance.
At the same time, wind shear is the key ingredient for tornadogenesis.
Video file
In most cases, wind shear causes hurricanes to weaken, but wind shear is always a necessary ingredient for tornadoes.
Environments with high wind shear allow small areas of rotation to form horizontally in the atmosphere. Robust updrafts help to orient those rotations vertically. Once thunderstorms form in this environment, they rotate like a barber pole, gradually lowering a wall cloud, then a funnel cloud, and ultimately a tornado.
Wind shear is especially enhanced in the outer bands of a landfalling hurricane, making tornadoes a real and common threat. Tornadoes most commonly form in the right-front quadrant of the hurricane where wind shear is the greatest.
Remarkable tornado outbreaks have occurred from hurricanes in the past.
- Hurricane Ivan in 2004 holds the record for the most tornadoes, with 117 being produced in the days after landfall.
- Hurricane Beryl produced three waves of tornadoes after landfall, primarily impacting Louisiana/Texas/Arkansas, Illinois/Indiana/Kentucky, and western New York.
- Hurricane Milton produced 46 tornadoes in South Florida alone in the hours before the eye officially made landfall.
- The strongest tornado caused by a hurricane is a tie: F4s (winds 207-260 mph) from Hurricane Carla (1961) and Hurricane Hilda (1964).
- The remnants of Ida in 2021 produced an EF-3 ‘wedge’ tornado in Mullica Hill, New Jersey. This is exceptionally rare in the mid-Atlantic/Northeast.
- Hurricane Harvey — in addition to the 60 inches of rain it dumped on Houston — dropped 29 tornadoes in the region and 86 tornadoes across the Southeast in total.
Next time a hurricane is landfalling, don’t forget that tornadoes are an overlooked hazard that are just as dangerous as others, even far from the eye.
Hurricane Season is a frightening time for many, and understandably so — it produces some of the strongest storms on Earth every year, disrupting homes, businesses, tourism, governments, and daily lifestyles.
We are taking a deeper dive into the four main hazards threatening communities when a hurricane strikes: wind, tornadoes, inland flooding, and storm surge. Although they pose a threat to human life and property in different ways, all four can happen simultaneously when a hurricane strikes.
Before we get to the hazards, however, it's important to understand some background information in hurricane forecasting and preparedness. What are the first things meteorologists look for before a hurricane is named? What are the different warnings when a hurricane strikes, and what do they mean? How do I know when exactly the storm will arrive, and how bad will it be?
Look no further — here’s how we know what to expect when a hurricane is brewing:
Start with the Tropical Weather Outlook
Long before a hurricane ever develops, Hurricane Specialists at the National Hurricane Center in Miami, FL, are watching the tropics for signs of tropical disturbances. These could be tropical waves, stalled cold fronts, or even remnants from a previous hurricane — any low pressure system over warm water that could become stronger.
When weather models begin to show that a disturbance may strengthen, the forecasters take notice. They mark the region with a low, medium, or high chance of development. Development typically means it becomes a tropical depression, the weakest form of a tropical system.
Video file
These forecasts are called ‘Tropical Weather Outlooks’ (TWOs). This is the first graphic that appears when you visit hurricanes.gov because, with one glance, you get a summary of all significant tropical weather in the entire Western hemisphere.
Once a tropical depression or tropical storm has formed, an official forecast is released to show how the storm will progress. This is often referred to as the ‘Forecast Cone,’ and it shows where the center of the storm is likely to track and how strong the storm may get. For the latest forecast on each storm, you can always visit hurricanes.gov .
If a depression grows to tropical storm strength (see wind article for this classification), it officially receives a name. These names are pre-set each season and updated by the World Meteorological Organization.
When a hurricane nears landfall
Now it is time to put your hurricane preparedness plan into action. Stay connected to your trusted source of information, as the weather conditions can be unpredictable and things could change rapidly. Communicate to your loved ones what your plans are so others can look out for you after the event is over.
Long before a hurricane impacts land, it can bring dangerous rip currents to coastal areas. This can occur even if the beach weather is sunny and the hurricane is hundreds of miles offshore. The NHC has new graphics that analyze the nation’s rip current risk here.
In the days leading up to landfall, Hurricane Watches and Tropical Storm Watches will be issued, identifying the regions that are likely to experience wind impacts from the storm within 48 hours.
When landfall is imminent (within <36 hours), Hurricane Warnings are posted in the locations that will experience hurricane-force winds from the storm.
Sometimes, there is confusion about the forecast cone and landfall. As a hurricane nears, the forecast cone shrinks because forecasters have a much better idea of where the center of the storm will track. It is important to keep in mind that impacts from a hurricane extend far from the center of the storm.
Conclusion
Now that you have a better understanding of where to find information when a hurricane threatens, you’re ready to learn about the main hazards a hurricane brings when it makes landfall.
Not everyone is familiar with the term storm surge. It often gets caught up with simpler terms like ‘high surf’ and ‘extreme flooding’, but these don’t give it the proper distinction it deserves.
Storm surge is historically the deadliest part of hurricanes, accounting for 49% of deaths from 1963-2012 (Rappaport, NHC 2014 offsite link).
Storm surge forecasting, awareness, and preparedness has improved by leaps and bounds in the last ten years, helping to bring the average death toll down significantly. Truly understanding what storm surge is and how it happens is the first step to creating a nation that is more prepared to battle a hurricane’s most powerful hazard.
What is it?
Simply put, storm surge is the rise in sea level associated with a hurricane. This rise can be feet above what the normal sea level would be, meaning it overtakes sea walls, sand dunes, and even buildings, flooding areas that are normally dry.
As a hurricane nears the coastline, its strong winds push ocean water onshore for hours on end. This can push ocean water well inland, including up rivers and bays, submerging communities miles away from the coast. Just two feet of surge can lift a vehicle, six feet stands taller than most people, and ten feet can submerge the first floor of homes. Check out this VR simulation.
What makes surge worse
Hurricane intensity is just one factor that plays into the severity of storm surge. Stronger winds have the ability to push more water, but the size and speed of a hurricane also play an important role.
Larger hurricanes — that is, those with a larger diameter of strong winds — blow more water towards shore. This translates to a more extensive storm surge along the coast. Pair this with a slow hurricane (moving at less than 10 miles per hour), and the ocean water is battered along the coastline relentlessly for hours, making a surge that moves farther inland.
A comparison that perfectly demonstrates this is between Hurricane Ian in 2022 and Hurricane Charley in 2004. They made landfall at the same strength, time, and location across southwestern Florida. Their only differences were speed and size: Charley was a small, fast-moving storm while Ian was large and slow-moving. The result was a devastating storm surge caused by Ian that took dozens of lives, and a minor storm surge from Charley. For more on this case study, visit this NHC blog post offsite link.
Location relative to the hurricane matters as well. The worst place for storm surge is usually just to the right of the hurricane's eye. Here, the strongest winds push the most water onto shore with the most force.
Small wobbles in a hurricane’s track can change a storm surge forecast tremendously. In 2024, if Hurricane Milton had moved just 20 miles north, it would have brought a devastating storm surge into the Tampa metro. Instead, it stayed far enough south to keep the surge mild.
Ocean bathymetry, the ocean floor’s shape, matters a bit too. Islands are generally protected from the worst surge because they typically have steep ocean floor shelves surrounding them. On the other hand, areas like the U.S. Gulf Coast have a gradual ocean floor that slopes up to the coast, meaning water can move easier and impact land sooner.
NHC storm surge unit
With all of these variables at play, the National Hurricane Center in Miami, FL, has its own Storm Surge Unit to independently analyze these risks for the entire U.S. and beyond. For every storm, the team forecasts how states, counties, and communities will be affected based on all the factors above.
Historic examples
- Hurricane Ian in 2022 produced storm surge up to 15 feet above normally dry ground in Fort Myers Beach, FL, bringing devastation to many vacation & retirement communities in the area.
- Hurricane Laura in 2020 brought storm surge up to 18 feet above normally dry ground along the western Louisiana coastline.
- Hurricane Camille in 1969 brought 24 feet above normal tide levels of storm surge to the Mississippi coast.
- Hurricane Katrina in 2005 holds the record for the highest storm surge ever recorded in the U.S. — a staggering 25-28 feet above normal tide levels.
In the last ten years, storm surge has lost its distinction as the deadliest hazard associated with tropical cyclones. This is partly thanks to more forecast information and a better public understanding of the phenomenon. Nonetheless, it is imperative to heed evacuation orders in storm surge zones when a hurricane arrives and to continue supporting public awareness of the hazard.
Video file
Counter-clockwise rotation of a hurricane means that the left side of the eye often experiences winds that push water away from shore. In 2017, Hurricane Irma caused this exact phenomena over Tampa Bay, draining out much of the water.
Hurricanes bring with them a lot of rain — that’s no secret. But once the storm weakens and moves inland, this rain becomes the leading killer.
Inland flooding broadens a hurricane’s danger to the millions of people who don’t live along the coast. Hurricanes can weaken to their “death,” yet the trillions of gallons of rain they brought with them remain. Tropical storms that do not reach hurricane status can still be very dangerous, causing heavy rainfall that increases the risk of inland flooding and mudslides in steep terrain.
Here, we explore what inland flooding looks like and how you can be prepared.
The immediate rain
On average, tropical cyclones bring more than 6 inches of rain to thousands of square miles after hitting land. This can quickly cause flooded roadways, swollen rivers, and dangerous flash floods — or floods that form in a matter of minutes.
While water rescue teams are prepared for this, there are often too many rescues for them to do in such inclement weather. This leads to residents becoming trapped in homes until the weather improves or until the water goes down. This can take days or even weeks.
How it becomes catastrophic
Inland flooding is exacerbated by three main factors: urbanization, topography, and concurrent weather systems.
Highly urbanized areas often have a difficult time draining off water thanks to concrete, which causes runoff rather than drainage. If draining systems are not properly located, cleaned, or designed, they can quickly back up and cause flooding in densely populated areas.
Topography is perhaps the biggest amplifier of heavy rains. Mountainous terrain funnels all water into nearby streams and rivers, causing them to swell quickly. This also loosens mountain soil, making landslides more likely to occur.
Finally, other weather systems can combine with a tropical cyclone or its remnants, adding to the total rainfall or simply ‘stalling’ the storm system. This causes it to sit over the same areas, bringing heavy rain for days on end that quickly overwhelm all waterways and drainage systems.
Why strength is not necessarily an indicator of rainfall amounts
Tropical cyclones — regardless of their strength — have an ability to hold extremely large amounts of water. All tropical cyclones form over the ocean, where the atmosphere is primed for holding water until it can’t anymore. The cycle is never ending, and any tropical system that makes landfall pushes all of this moisture over land.
That is why the strength of a tropical depression, tropical storm, or hurricane at landfall is not the most important factor when it comes to rainfall potential.
‘PWAT’, or Precipitable Water, is a measurement describing how deep the water would be if all the water vapor in a column of air turned to rain. The average global PWAT offsite link is 0.85 inches (generally dry), while hurricanes can have PWAT values over 3 inches (extremely saturated).
Historic examples
The most recent example of deadly inland flooding came from Hurricane Helene in 2024. Before Helene made landfall, a cold front brought 4-6 inches of rain across the Appalachian Mountains of North Carolina. After Helene made landfall in Florida, it travelled northward into that very region, where it combined (or merged) with another area of low pressure associated with a prior system. This caused days of heavy rain on top of already-saturated soil, leading to a flooding catastrophe in the region. 107 fatalities occurred in the region alone.
In 2021, Hurricane Ida made a devastating Category 4 landfall in Louisiana. However, the worst of the flooding came in the Northeast. Up to ten inches of rain fell along the I-95 corridor, leading to historic flooding across the region. New York City saw dozens of apartment building basements flooded while residents struggled to escape. 43 people lost their lives across the Northeast even though it was only Ida’s remnants that moved through the area.
In 2017, Hurricane Harvey rewrote the record books. A Category 4 landfall was only the start of a nightmare for southeast Texas. Harvey ‘stalled’, or remained stationary, for over four days. Rain totals over 60 inches were recorded, flooding the Houston metro and all surrounding areas. The storm cost $160 billion, making it the 2nd costliest of all time, only behind Hurricane Katrina in 2005.
Even six inches of flood water can sweep an adult off their feet, and as little as one foot of water can float a vehicle.
When people think of a hurricane, the first hazard that comes to mind is the wind. Tropical cyclones are classified based on their maximum sustained winds, and hurricanes specifically are rated according to the Saffir-Simpson Wind Scale. The raw power of these winds pose a multitude of hazards to life and property.
Here, we’ll break down what different wind speeds mean and how they might affect your community.
Tropical depression
As an area of low pressure strengthens, so do its winds. When a tropical cyclone has sustained winds below 39 mph (34 knots), it is considered a tropical depression.
Tropical storm
When winds reach 39 mph (34 knots) or more, a depression is reclassified as a tropical storm. At this point, a name is given to the system. For a complete list of tropical storm & hurricane names each year, and a look at how these names are decided, visit the National Hurricane Center's Tropical Cyclone Names page.
When a tropical storm is confirmed to have sustained winds of 74 mph (64 knots) or greater, the system is reclassified as a hurricane.
The highest 1-minute average wind that is found in a tropical cyclone at a particular time. These are not wind gusts, but rather winds that are constantly blowing at/near a certain speed. It is the standard measure of a tropical cyclone's intensity in the Atlantic and Eastern/Central Pacific basin.
The saffir-simpson wind scale
The Saffir-Simpson Wind Scale is a rating system that ranges from 1 to 5 and is based solely on the maximum sustained wind speed of a hurricane. It is important to note that this scale considers only wind hazards and does not account for storm surge, rainfall flooding, or tornadoes. For more information about the Saffir-Simpson Wind Scale, please see this detailed description (PDF)
In strong winds, debris can quickly become projectiles and pose a danger to life and property. The winds can affect areas along the coast or far inland. In 2024, Hurricane Helene struck the Big Bend of Florida, causing extensive damage on the coast as well as inland across the southeastern states. Hurricane-force wind gusts brought down many trees across Georgia and the Carolinas — areas with dense tree canopies — causing extensive power outages and dozens of fatalities.
Products available from the National Hurricane Center
The National Hurricane Center provides wind probabilities that indicate the likelihood that winds will reach tropical storm force or hurricane force at specific locations along the storm's path. As the system approaches, these probabilities increase or decrease based on improved forecasts.
It is crucial to not underestimate the power of the winds associated with tropical systems. Recognizing that dangers extend far from the storm’s center is essential to preparedness and safety. As always, visit hurricanes.gov to see your wind forecast when a storm nears.
Tornadoes and hurricanes: different storms at the same time
Tornadoes are sometimes thought to be a problem of the high plains — most commonly, the infamous “Tornado Alley.” Yes, twisters are common here, but it is certainly not the only place they occur.
As a matter of fact, tornadoes often occur in hurricanes.
Hurricanes are nature’s finest display of power, made by a shield of convective counterclockwise rotation. The scale of this circulation is massive — spanning hundreds of miles across — and dwarfs the size of the average tornado, which is 50 yards across.
We speak about a tornado in a hurricane because the tornado forms under the umbrella of the hurricane’s broad rotation, not just near it. However, these tornadoes still originate from their own complex rotation and dynamics, independent of the hurricane’s. The hurricane just provides the perfect environment for tornadoes to occur.
It all starts when a hurricane comes close to land.
This dramatic shift from the warm ocean waters to Earth’s rocky terrain means that hurricanes encounter a completely different environment. The warm, moist air above the ocean surface is replaced by a turbulent and comparatively dry air above land. Winds that once blew freely over the sea encounter hills, mountains, buildings, and drag over land. The ocean is a hurricane's sole fuel source, and upon landfall, it is completely cut off.
This process causes the hurricane to experience wind shear. Wind shear is a change of wind speed and/or direction with height in the atmosphere. It is the death of hurricanes, causing their vertically-stacked eyewall to become tilted and off balance.
At the same time, wind shear is the key ingredient for tornadogenesis.
Video file
In most cases, wind shear causes hurricanes to weaken, but wind shear is always a necessary ingredient for tornadoes.
Environments with high wind shear allow small areas of rotation to form horizontally in the atmosphere. Robust updrafts help to orient those rotations vertically. Once thunderstorms form in this environment, they rotate like a barber pole, gradually lowering a wall cloud, then a funnel cloud, and ultimately a tornado.
Wind shear is especially enhanced in the outer bands of a landfalling hurricane, making tornadoes a real and common threat. Tornadoes most commonly form in the right-front quadrant of the hurricane where wind shear is the greatest.
Remarkable tornado outbreaks have occurred from hurricanes in the past.
- Hurricane Ivan in 2004 holds the record for the most tornadoes, with 117 being produced in the days after landfall.
- Hurricane Beryl produced three waves of tornadoes after landfall, primarily impacting Louisiana/Texas/Arkansas, Illinois/Indiana/Kentucky, and western New York.
- Hurricane Milton produced 46 tornadoes in South Florida alone in the hours before the eye officially made landfall.
- The strongest tornado caused by a hurricane is a tie: F4s (winds 207-260 mph) from Hurricane Carla (1961) and Hurricane Hilda (1964).
- The remnants of Ida in 2021 produced an EF-3 ‘wedge’ tornado in Mullica Hill, New Jersey. This is exceptionally rare in the mid-Atlantic/Northeast.
- Hurricane Harvey — in addition to the 60 inches of rain it dumped on Houston — dropped 29 tornadoes in the region and 86 tornadoes across the Southeast in total.
Next time a hurricane is landfalling, don’t forget that tornadoes are an overlooked hazard that are just as dangerous as others, even far from the eye.