Idaho Snowpack & River Runoff

Snow-water equivalent by basin and the seasonal runoff outlook for Idaho'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.

Idaho's snowpack is running thin this year — the statewide figure of 22% of normal means runoff peaked early and summer flows will thin out faster than usual. The higher-elevation freestones won't fish for long; tailwaters and spring creeks will carry more of the season.

If you're planning trips this year, bias toward tailwaters with cold dam releases and spring creeks that aren't snowmelt-driven. Smaller freestones in the lower elevations may warm into marginal water by mid-summer.

Basin SWE vs. median — water year 2026

Average across the Idaho basins we track, in inches of snow-water equivalent.

3 Idaho rivers tracked

River	Region	Basin snowpack	SWE now / normal	Median melt-out	Runoff forecast
Salmon River	Central Idaho	41%of normal	5.4" / 13.3"	~Jun 28	77%May–Jul · 3.8M acre-ft
Henry's Fork	Eastern Idaho	3%of normal	0.3" / 9.2"	~Jun 4	68%May–Jul · 235k acre-ft
South Fork Snake River	Eastern Idaho	—	0.0" / 0.0"	~May 12	75%May–Jul · 2.0M 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 Idaho figure is statewide, not specific to any one basin. Snowpack varies with elevation and aspect — treat basin figures as a guide. Updated May 17, 2026.

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