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

Examples 

• 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