SnowLoadCheck

Dawson County, MT Roof Snow Load - 20 psf

Dawson County, MT: your roof's ASCE 7 snow number, in plain English

Moderate
20 psf

Dawson County's roofs are built to hold 20 psf of snow, the ASCE 7-22 figure a permit reviewer checks first. The physics-based figure alone would be 17.5 psf, but ASCE 7's own low-slope minimum (§7.3.4) sets a floor of 20 psf for flat and low-pitch roofs here, which is the number that actually governs.

In depth, not weight: that's roughly 44 inches of fresh, light snow, 16 inches of old, settled snow, or as little as 4 inches of solid ice - snow that heavy is rare here but ice from a freeze-thaw cycle adds up far faster than the depth suggests. This is a meaningful design load - most modern-code homes handle it fine, though an addition, a carport or a flat-roofed section can be a weak spot.

Dawson County at a glance

Dawson County by the numbers

Nationally that's #1,132 out of 2,758 rated counties, the top 41%; within Montana alone, Dawson County ranks #14 of 29. 19 psf is Montana's typical county figure - Dawson County beats it by 1 psf.

Dawson County, FIPS 30021, is home to 8,731 people near 47.2661°N 104.8983°W. Its 25 psf ground snow load figure is the map value; 20 psf is what a roof is actually designed for.

Dawson County's snowfall, most winters

10.8 in. a year: that's Dawson County's NOAA 1991-2020 snowfall normal, measured at HOYT 2 WSW, MT US (24 mi away). See the density guide.

Before you rely on Dawson County's number

Treat the Dawson County figure as a starting point, not a final answer: it assumes standard occupancy, a heated structure and a moderately sheltered site, per ASCE 7-22's own defaults. Exposed terrain, an unheated building or a steeper roof all shift the real number.

For a real application, skip the county number and go straight to the ASCE 7 Hazard Tool - enter your coordinates and it returns a site-specific figure a plan reviewer will recognize. (How this figure is calculated.)