Streamflow, Drought, and Water Supply Conditions

Water supply conditions as of 5/1/2019

From The montana water supply outlook report

Jefferson Basin: “April wasn’t quite as kind to the Jefferson River basin as it was to the basins surrounding it. Storms during the middle two weeks of the month favored the northern half of the river basin, helping to increase only the high elevation snowpack in the basin. Low and sites made the transition to melt this year in late March, and mid-elevations were able to hold on until the anomalously warm weather during the third week in April. Many high elevation sites still haven’t made the transition to melt but will once the weather returns to more seasonal patterns. Snowpack at peak accumulation at most sites was near to slightly below normal this year, but new peaks may yet be set at high elevations. Overall basin-wide snowpack for this date remains slightly below normal for May 1st, due in large part to the early low elevation melt. The good news is that as of May 1st, both Clark Canyon and Ruby reservoirs are both full, but summer demand and the rate of inflow from the higher elevations will dictate how much water is available later in the summer months. Streamflow forecasts for the May 1st – July 31st period range from below average in the Red Rock/Upper Beaverhead basin to near to slightly below average in the Big Hole and Lower Jefferson River basins.”

Big Hole Sub-basin Snowpack: 96% of normal (1981-2010 median)

Period of Record Monthly Climate Summary – Period of Record : 01/01/1923 to 06/09/2016

See details below from Western Regional Climate Center:


Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Average Max. Temperature (F) 26.4 31.1 38.5 49.2 60.3 68.6 79.4 77.8 67.6 55.0 38.0 28.0 51.7
Average Min. Temperature (F) 1.2 3.3 10.8 21.2 28.7 36.1 38.2 34.7 27.8 21.3 12.3 3.6 19.9
Average Total Precipitation (in.) 0.70 0.52 0.74 0.95 1.64 1.96 1.09 1.03 0.99 0.83 0.76 0.77 11.97
Average Total SnowFall (in.) 11.8 8.3 8.6 4.5 2.5 0.5 0.0 0.0 0.5 1.9 7.8 10.8 57.0
Average Snow Depth (in.) 9 10 8 1 0 0 0 0 0 0 2 5 3

Percent of possible observations for period of record.
Max. Temp.: 98.7% Min. Temp.: 98.6% Precipitation: 98.6% Snowfall: 76.4% Snow Depth: 50.3%


National Water Supply Reports

Nation-wide information for water supply and climate prediction & forecasts. 

National Weather Service Climate Prediction Center – Three Month Outlook Report


Montana Water Supply Reports & resources

Statewide information for water supply and drought conditions. Report breaks out conditions by major basins:

Montana Water Supply Outlook Reports

Guide to Using the New Montana Water Supply Report

Water supply and drought condition information specific to the Upper Missouri Basin:

Upper Missouri River Basin

Water Monitoring Resources from the Montana Watershed Coordination Council

Montana Watershed Coordination Council Water Monitoring webpage


Past Streamflow & Snowpack Reports

February 2019 Streamflow/Snowpack Report (PDF)

November 2018 Streamflow/Snowpack Report (PDF)

October 2018 Streamflow/Snowpack Report (PDF)

September 2018 Streamflow/Snowpack Report (PDF)

June 2018 Streamflow/Snowpack Report (PDF)

May 2018 Streamflow/Snowpack Report (PDF)

April 2018 Streamflow/Snowpack Report (PDF)

March 2018 Streamflow/Snowpack Report (PDF)

February 2018 Streamflow/Snowpack Report (PDF)

November 2017 Streamflow/Snowpack Report (PDF)

October 2017 Streamflow/Snowpack Report (PDF)

August 2017 Streamflow/Snowpack Report (PDF)

June 2017 Streamflow/Snowpack Report (PDF)

April 2017 Streamflow/Snowpack Report (PDF)

March 2017 Snowpack Report (PDF)

February 2017 Snowpack Report (PDF)

November 2016 Streamflow/Snowpack Report (PDF)

September 2016 Streamflow/Snowpack Report (PDF)

May 2016 Streamflow/Snowpack Report (PDF)

April 2016 Streamflow/Snowpack Report (PDF)

March 2016 Streamflow/Snowpack/CCAA Report (PDF)

February 2016 Streamflow/Snowpack Report (PDF)