Update to U.S. precipitation frequency standards now accounts for climate trends

A key scientific NOAA resource on extreme precipitation that is widely used by floodplain managers, city planners, civil engineers, developers and communities across the nation will soon include climate trend data. 

NOAA’s Precipitation Frequency Atlas of the United States (Atlas) provides the statistical likelihood of an extreme precipitation event at a particular location in any given year, which — until recently — assumed a stationary climate. These statistics are the basis for planning and infrastructure design and for communicating the likelihood of extreme events, such as storms that have a 1% chance of occurring. 

Recognizing that extreme precipitation and nationwide flood risk are getting worse in a warming climate, NOAA is changing the methodology used to produce the Atlas by factoring the future state of the climate into official precipitation frequency estimates. With the first-ever direct federal funding for an update, funding from the Bipartisan Infrastructure Law will allow NOAA to develop Atlas 15, an update to the NOAA Atlas 14 precipitation frequency nationwide standard, to account for future climate conditions.

“Atlas 15 will become the federal government's new authoritative dataset for the planning and design of infrastructure Americans rely on every day,” said Ed Clark, director of NOAA’s National Water Center. “With the increasingly complex water challenges facing the nation, Atlas 15 will build upon the foundational Atlas 14 standard and provide an equitable service for all communities seeking to become more climate resilient.” 

Beginning with a pilot project for the state of Montana, today, NOAA released an early look at the data used to produce Atlas 15 Volumes 1 and 2 to get stakeholder feedback before expanding nationwide. Volume 1 uses trends in observations and Volume 2 uses climate model output data to estimate future conditions. 

Stakeholders are asked to review and compare both volumes and provide feedback on the utility of each interface. Doing so will be the first step in a robust peer-review process that Atlas 15 will undergo before it is published for the continental U.S. in 2026, and the rest of the country in 2027. Next year, NOAA will release preliminary estimates for the lower 48 states to begin the peer review process. When Atlas 15 is published, these data will provide communities across the country with information necessary to adapt to future climate conditions. 

NOAA precipitation frequency estimates are recognized by the engineering and floodplain management communities as the authoritative source of precipitation frequency data due to the rigor of the scientific methods and quality control applied, the extensive amount of data included in the analysis and the thorough peer review process conducted with a vast array of stakeholders. 

With this early release for Montana, NOAA encourages stakeholders, including engineers, city planners and climate scientists, to provide feedback on the pilot data offsite link. Their input will help shape the final dataset, ensuring it meets the needs of communities nationwide.

Climate, weather, and water affect all life on our ocean planet. NOAA’s mission is to understand and predict our changing environment, from the deep sea to outer space, and to manage and conserve America’s coastal and marine resources.