Madison County, MT Roof Snow Load - 10 psf
What ASCE 7 says about snow load in Madison County
That's Madison County's design roof snow load per ASCE 7-22, for a typical heated single-family home - the number a permit reviewer starts from. The physics-based figure alone would be 7 psf, but ASCE 7's own low-slope minimum (§7.3.4) sets a floor of 10 psf for flat and low-pitch roofs here, which is the number that actually governs.
Converted to something you can actually eyeball on a roof: about 22 in. of fresh powder, 8 in. once it settles and packs down, or just 2 in. if it's turned to ice. A modest addition to standard roof loading. Ordinary residential construction handles this without extra bracing.
Madison County at a glance
- Design roof snow load10 psf
- Ground snow load, ASCE 7 map10 psf
- National rank#2,002 of 2,758
- Montana rank#29 of 29
- Population9,753
- Annual snowfall, NOAA normal44.7 in.
- FIPS30057
Where Madison County's figure sits nationally
Out of 2,758 rated US counties, Madison County sits at #2,002, the top 73% nationally - #29 of 29 within Montana. 19 psf is Montana's typical county figure - Madison County comes in 9 psf under it.
Near 45.3253°N 111.9138°W, FIPS 30057: Madison County counts 9,753 residents and a 10 psf map value, which the code's own factors turn into 10 psf.
How much it actually snows in Madison County
Most winters bring Madison County roughly 44.7 in. of snow - NOAA's normal at ENNIS, MT US, 9.8 mi off. (fresh vs. packed vs. ice explains why.)
Read this before you rely on it
Madison County's number above is ASCE 7-22's default case, not a custom calculation: ordinary residential occupancy, heated, sited on ground that's neither fully sheltered nor fully exposed. Any one of those changing - pitch, exposure, heating, occupancy - moves the real figure.
Nothing here substitutes for an address-level number. Get one free, in about a minute, from the ASCE 7 Hazard Tool using your own coordinates rather than Madison County's county-wide figure. (How this figure is calculated.)