Montana Snowpack & River Runoff

Snow-water equivalent by basin and the seasonal runoff outlook for Montana's rivers, translated into what it means for fishing — early or late runoff, high or low summer flows, and which waters hold up best. Updated daily through the snow season.

7 Montana rivers tracked

River	Region	Basin snowpack	SWE now / normal	Median melt-out	Runoff forecast
Madison River	Southwest Montana	45%of normal	8.3" / 18.5"	~Jun 24	76%May–Jul · 390k acre-ft
Yellowstone River	Southwest Montana	53%of normal	4.2" / 8.0"	~Jun 18	84%May–Jul · 1.5M acre-ft
Missouri River	Central Montana	63%of normal	10.0" / 15.8"	~Jun 24	63%May–Jul · 965k acre-ft
Gallatin River	Southwest Montana	69%of normal	16.5" / 23.9"	~Jun 24	73%May–Jul · 270k acre-ft
Bitterroot River	Western Montana	71%of normal	7.9" / 11.2"	~Jun 11	95%May–Jul · 365k acre-ft
Bighorn River	South Central Montana	73%of normal	9.1" / 12.5"	~Jun 20	58%May–Jul · 860k acre-ft
Big Hole River	Southwest Montana	112%of normal	16.9" / 15.1"	~Jul 1	84%May–Jul · 350k acre-ft

Runoff forecasts are the projected seasonal streamflow volume versus the long-term average, issued monthly January–June. Only rivers with a published forecast point show one.

Snowpack percentages compare current basin snow-water content to historical norms; the Montana figure is statewide, not specific to any one basin. Snowpack varies with elevation and aspect — treat basin figures as a guide. Updated May 13, 2026.