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Historic Data

The National Weather Service (NWS), NOAA, is a source of data provided in some of these products.

Historic SNOTEL Update Reports

Historic Daily SNOTEL Data

Historic Monthly SNOTEL and Snow Course Data

Historic Monthly Precipitation Basin Reports

Historic Monthly Precipitation Tables

  • Idaho Data Collection Office Area SNOTEL sites (Idaho, western Wyoming, northern Nevada, eastern Washington) - Period of Record Monthly Precipitation:


  • Idaho NWS and COOP sites - Period of Record Monthly Precipitation:



Historic Monthly Reservoir End of Month Storage Tables


Historic Monthly Adjusted Streamflow Tables

Data in these tables for streams with major reservoirs have been adjusted by adding upstream reservoir change-in-storage volumes and major diversions to the observed monthly streamflow volumes to reflect a "natural flow" condition.  Reservoir evaporation and most diversions are not accounted for in the NRCS database listed here.  The U.S. Geological Survey (USGS),  U.S. Bureau of Reclamation (USBR) and Idaho Department of Water Resources (IDWR) are a source of most of the data presented.  Streams without reservoirs and stations upstream of the reservoirs show monthly data as received directly from USGS archived records.


Historic Snow Indexes for Idaho Basins

What is a snow index?

Snow Graphs - Illustrating the Chance of Snowpack to Recover by April 1 -These snow graphs are sorted from low to high, first of month SWE for January, February, and March with comparisons to how the winter accumulation season ended on April 1.  The graphs are based on the historic snow index data listed above.

Historic Monthly Map Products

  • Idaho First of Month Snowpack Maps  
  • Idaho First of Month Streamflow Forecast Maps: