Map: monthly average precipitation

This map shows total rain and snowfall in the contiguous United States, every month from 1981 to the present. The map’s color scale runs from white (no precipitation), to blue (significant precipitation) to red (intense precipitation).

The resolution of the data is about 800 meters (around a half-mile) per pixel. For the purposes of download time, the resolution of the image on the map has been reduced to four kilometers per pixel (about 2.5 miles). 

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Data on precipitation in the Contiguous U.S. is taken from the PRISM Climate Group at Oregon State University, which uses weather station data and a sophisticated interpolation model to produce monthly and daily precipitation for the contiguous U.S. at about 800-meter resolution. 

For the most recent six months of data, we use their provisional data, and their more stable data for earlier months. We use these data to calculate monthly totals each state, and monthly averages since 1981.

See this post to learn more about this dashboard and other interactive visualizations.

The Water Desk’s mission is to increase the volume, depth and power of journalism connected to Western water issues. We're an initiative of the Center for Environmental Journalism at the University of Colorado Boulder. The Water Desk launched in April 2019 with support from the Walton Family Foundation. We maintain a strict editorial firewall between our funders and our journalism. The Water Desk is seeking additional funding to build and sustain the initiative.