Custer County, MT Roof Snow Load - 20 psf
Custer County, MT: your roof's ASCE 7 snow number, in plain English
Custer County's roofs are built to hold 20 psf of snow, the ASCE 7-22 figure a permit reviewer checks first. Flat and low-pitch roofs in Custer County are actually governed by ASCE 7's §7.3.4 minimum of 20 psf, not the 17.5 psf the ground-load formula alone would produce.
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.
Custer County at a glance
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#1,071 of 2,758
- Montana rank#11 of 29
- Population11,964
- Annual snowfall, NOAA normal29.9 in.
- FIPS30017
Custer County by the numbers
Nationally that's #1,071 out of 2,758 rated counties, the top 39%; within Montana alone, Custer County ranks #11 of 29. 19 psf is Montana's typical county figure - Custer County beats it by 1 psf.
Custer County, FIPS 30017, is home to 11,964 people near 46.2614°N 105.5504°W. Its 25 psf ground snow load figure is the map value; 20 psf is what a roof is actually designed for.
Custer County's snowfall, most winters
29.9 in. a year: that's Custer County's NOAA 1991-2020 snowfall normal, measured at POWDERVILLE 8 NNE, MT US (37.5 mi away). 37.5 mi is a real gap between Custer County and its nearest reporting station, so local snowfall can diverge from this figure, especially near elevation changes. See the density guide.
Before you rely on Custer County's number
Treat the Custer 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. Details: the calculation guide.