Lewis and Clark County, MT Roof Snow Load - Case Study Area
Lewis and Clark County, MT: no map figure, on purpose
ASCE 7's own snow load map has no single figure for Lewis and Clark County: the terrain is complex enough that the code (§7.2) requires an elevation-specific study rather than a county-wide value. That is the map being accurate, not a data gap.
FIPS 30049, population 75,129. 386 US counties get this same case-study treatment; Lewis and Clark County is one of them.
Lewis and Clark County, MT: quick facts
- Population75,129
- Annual snowfall, NOAA normal45.9 in.
- FIPS30049
Lewis and Clark County: average annual snowfall
Lewis and Clark County sees about 45.9 in. of snow most winters, per the SIMMS 1 NE, MT US station's 1991-2020 NOAA normal. 33.9 mi is a real gap between Lewis and Clark County and its nearest reporting station, so local snowfall can diverge from this figure, especially near elevation changes. See the density guide.
Read this before you use Lewis and Clark County's figure
The figure above assumes the case ASCE 7-22 treats as typical: a heated, ordinary-occupancy home on a partially exposed site. Change any of those - exposure, heating, roof pitch, occupancy category - and the real design number moves.
A building permit needs the number at your exact address, not the county average - the free ASCE 7 Hazard Tool returns that from your coordinates in about a minute and produces a PDF a plan reviewer will accept. (How this figure is calculated.)