Mean Monthly and Annual Precipitation
Conterminous United States

Statistic: 30-year average total precipitation 
Time period: 1961-1990
Time interval: monthly
Spatial format: grid
Data format: ARC/Info ASCII GRID

Projection: Geographic
Spatial resolution: 1.25 arc-minutes (~2 km)
Spatial Extent: Conterminous United States
Date created: August 2000
Methods: The PRISM modeling system and Gaussian filter resolution enhancement.
See FGDC-compliant metadata for details.


Mean annual precipitation, entire region
Mean annual precipitation, southern Idaho
  • Accepted by the US Department of Agriculture as the official precipitation maps for the United States 
  • Peer reviewed by experts nationwide 
  • Incorporates topographic effects on precipitation 
  • Captures rain shadows in great detail 
  • Includes coastal and lake effects on precipitation 
  • Accounts for the varying ability of terrain features to enhance precipitation 
  • Consistent treatment and spatial quality control of station data 
  • Consistent coverage across all state boundaries 
  • "Universal" geographic (latitude/longitude) projection allows conversion to any other coordinate system 
  • Data format allows for easy import into ESRI's GIS products, as well as MAPINFO and Intergraph's GeoMedia 

Data used in analysis

  • 9,110 Stations 
  • 7,700 National Weather Service stations 
  • 570 USDA Natural Resources Conservation Service SnoTel stations 
  • 640 Supplementary stations, including national forest gauges, snow courses, and remote storage gauges 
  • 200 Canadian stations
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