Peak snowpack is the single most important number in the mountain water year. Everything that follows — spring runoff, summer river flows, reservoir fill, wildfire risk — is downstream of it, literally and figuratively. The 1991–2020 NRCS normal tells us when that peak should arrive and how deep it should be. The 2025–26 season tells a different story: a record-warm winter that forced early peaks across basin after basin, and where those peaks arrived, they fell well short of normal.
What "Normal Peak" Actually Means
The NRCS has been using April 1 as the standard snowpack benchmark date for water supply forecasting since the early days of the snow survey program. The logic was simple: across most of the West, April 1 historically coincided closely with peak SWE at a majority of stations. If you could measure how much water was stored in the snowpack on that date, you could make a reasonably accurate forecast for spring and summer streamflow.
The 1991–2020 normal codifies this in a more nuanced way. Rather than a single benchmark date, the NRCS now characterizes peak SWE by basin, acknowledging that different terrain peaks at different times. In the northern Rockies — Montana, northern Idaho, and the Bitterroot — the median peak typically arrives somewhere between late March and late April depending on elevation and aspect. High-elevation basins in the Wind Rivers and Absarokas of Wyoming hold on into May. Lower-elevation and south-facing terrain often peaks in early-to-mid March. The spread across the region spans nearly two months.
The 1991–2020 median is also lower at many sites than the previous 1981–2010 period, reflecting a documented trend toward lighter and earlier snowpack across the northern Rockies. What reads as 100% of current normal may still represent a below-average season in an absolute, multi-decade sense. That context matters when interpreting this year's data.
The Normal Peak Map: What the 30-Year Average Looks Like
The map below shows the 1991–2020 median peak SWE for SNOTEL stations across the northern Rockies and surrounding region. Station size reflects the depth of that median peak — deeper snowpacks in the upper Cascades, coastal ranges, and high-elevation interior are immediately visible. The coloring indicates when during the water year each station typically hits its maximum, from early-peaking lower-elevation sites in February and March through the high-country stations that don't max out until April or May.
1991–2020 Median Peak SWE by SNOTEL Station · Size = peak depth · Color = typical peak timing · Data: USDA NRCS via OutsideDB
The spatial pattern reflects the West's basic orographic logic: the deepest snowpacks are where Pacific moisture meets the highest terrain. In the northern Rockies, the Bitterroot divide, the Cabinet Mountains, and the ranges straddling the Montana-Idaho border consistently produce the deepest median peaks — often exceeding 30 to 40 inches of SWE at the highest stations. The Absaroka-Beartooth front in south-central Montana and the Wind Rivers in Wyoming follow a similar pattern but with a later peak timing due to their more continental exposure. Lower-elevation stations across eastern Montana and the high plains flats register minimal median peaks, sometimes just a few inches of SWE before the spring sun terminates the season.
The 2025–26 Season: Warmth Forced Everything Early
The 2025–26 water year will be remembered as one of the warmest on record across the West. California, Idaho, and Montana each recorded their second warmest winter since widespread SNOTEL records began in the early 1980s. Arizona and New Mexico broke previous winter temperature records by over 2°F. The consequences for snowpack were severe and direct: precipitation that fell warm came as rain rather than snow at low and mid elevations, early-season rain-on-snow events melted existing snowpack, and the cold windows needed to build and hold snow were abbreviated or absent.
By early February, records across the network showed the vast majority of western SNOTEL stations reporting below-median SWE, with Idaho, Utah, Colorado, and Oregon among the states recording their lowest statewide snowpack since records began. The West was not simply below normal; at many stations it was at record or near-record lows.
The mid-March atmospheric river brought meaningful relief to parts of the northern Rockies, with stations in the upper Clark Fork and Yellowstone headwaters climbing noticeably. But the storm largely missed southwestern Montana, the Madison and Gallatin drainages, and the Yellowstone plateau — the basins that were already most stressed heading into spring.
This Year's Peak Snowpack Map
The map below shows where the 2025–26 season peak SWE was recorded at SNOTEL stations across the West, compared against the 1991–2020 normal. Stations are colored by percent-of-normal-peak — blue indicates above-normal, yellow through red indicates below.
2025–26 Season Peak SWE vs. 1991–2020 Median Peak · Blue = above normal · Red = below normal · Data: USDA NRCS SNOTEL via OutsideDB · Late-season stations may still be accumulating
The geographic pattern is broad and largely follows the season's storm track story. The northern interior ranges — the high-elevation spine from the northern Cascades through western Montana — show the strongest relative performance, having caught the mid-March atmospheric river and holding temperatures cold enough to bank that moisture as snow. Moving south and west, the picture deteriorates: the Oregon and California ranges, much of the Great Basin, and the southern Rockies are predominantly in deficit territory. Even within states, the contrast is sharp — some high-elevation stations in the Absarokas and Wind Rivers in Wyoming held near or above normal while lower basins in the same drainages had already peaked and were losing ground. The lower-elevation stations across the interior Pacific Northwest and Snake River Plain are largely in the red, having run their course well below normal.
What This Means Heading Into Spring
Basins that peaked early and below normal are not going to recover. A snowpack that hit its maximum in mid-March and has been melting since then does not get rebuilt in April — temperatures are rising, solar radiation is intensifying, and the physics don't allow it. What those basins will deliver in terms of spring runoff is already determined. The question is whether the snowmelt pulse comes fast (flood risk, then drought) or slow (sustained river flows into early summer). That depends on the April weather.
For the basins still near or potentially above normal — upper Clark Fork, Yellowstone headwaters, some of the high-elevation stations along the northern divide — the coming weeks matter enormously. A warm, dry late March and April would pull those basins down fast and compress the runoff into a short window. A cooler, wetter pattern could extend the accumulation season and push peak dates toward historical norms.