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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.


Historical Snow Indexes and Snow Graphs for Idaho Basins

Measuring the amount of water held in the mountain snowpack in a given basin provides a better understanding of water supply and, in some cases, a better understanding of 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. Daily measurement data are recorded at SNOTEL sites in or near the watershed divide for each basin. Monthly indexes are calculated by summing first of the month values of snow water content for each of the long-term sites in the basin.

Historic Monthly Map Products

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