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Monitoring of heavy precipitation events: interactive maps

These images show locations where average recurrence intervals for precipitation have been exceeded. These are referred to, for example, as "100-year rainstorms", though this terminology can cause confusion, so a more accurate description is "less than a 1% probability of occurring at a given location in any given year." This is an automated search for the types of events discussed in Schumacher and Johnson (2005, 2006) and Stevenson and Schumacher (2014), using gridded precipitation analyses, as well as updated to use NOAA's Atlas 14 to define the average recurrence intervals. (In the states of Washington and Oregon, Atlas 14 has not yet been updated, so no points are shown.)

Each dataset has been regridded to a 4-km latitude-longitude grid (the same grid used by the PRISM Climate Group) prior to calculating the exceedance points. This allows for a closer "apples-to-apples" comparison between precipitation datasets. These maps are interactive (you can zoom in, and hover over a point to see the date, location, and amount.) They will be best used on a desktop or tablet (navigation of the interactive maps on a mobile phone is not ideal.)

31 December 2024: interactive maps updated to version 1.1, which includes the CoCoRaHS and CONUS404 datasets, and uses the 2024 update of Atlas 14 in the interior northwest (Montana, Idaho, and Wyoming.) CoCoRaHS observations come from volunteer precipitation observers. CONUS404 is a downscaled version of the ERA5 reanalysis at 4-km grid spacing.

Select dataset: Stage IVPRISMCoCoRaHSCONUS404      Near-real-time maps  Static maps of past events
Select average recurrence interval: 1000-year100-year
Select accumulation period: 24 hr48 hr72 hr
Select color scheme: by monthby year
Select start year: 2002

DISCLAIMER: The images and data on this site are intended for meteorological education and research purposes and, although they should generally be up to date, are not monitored at all times. Do not use for making decisions where money or lives are at stake. For official forecasts and warnings, visit the National Weather Service.