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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.


Snow Graphs - Illustrating the Chance of Snowpack to Recover by April 1

Snow graphs illustrate average monthly snow water and the chance of snowpack “recovery” for a given year. Snowpack recovery refers to the chance that snow water content will increase to reach average peak seasonal values (typically April) when accumulation is below average during core winter months (typically Nov-Feb). Data are sorted from low to high snow water, using first of the month values for January, February, and March to compare across the accumulation season, ending on April 1st. Stream flow graphs are included to show a simplified relationship between seasonal snow water and stream flow. Flow data is sorted by the month of April to illustrate peak of season patterns and sorted by year for comparison purposes.

Snow Indexes, Historic Snow Water Data by Basin, Idaho

Measuring the amount of water held in the snowpack in a given basin helps to better understand water storage and, in some cases, potential runoff volumes during the spring and summer months. Indexing the snow water values allows for easy comparison from year to year and for observing trends over time.

Panhandle Region Basins
Clearwater River Basin
Salmon River Basin
Weiser, Payette, Boise Basins
Wood and Lost River Basins
Upper Snake River Basin
Southside Snake River Basins
Bear River Basin

Historic Monthly Map Products

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