Pennington County, SD Roof Snow Load - 20 psf
Pennington County, SD: your roof's ASCE 7 snow number, in plain English
Pennington 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 14 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. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.
Pennington County in numbers
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#634 of 2,758
- South Dakota rank#58 of 65
- Population115,979
- Annual snowfall, NOAA normal48.5 in.
- FIPS46103
Pennington County by the numbers
Nationally that's #634 out of 2,758 rated counties, the top 23%; within South Dakota alone, Pennington County ranks #58 of 65. South Dakota counties average 28.2 psf; Pennington County runs 8.2 psf lower than that.
Pennington County, FIPS 46103, is home to 115,979 people near 44.0023°N 102.8238°W. Its 20 psf ground snow load figure is the map value; 20 psf is what a roof is actually designed for.
Pennington County's snowfall, most winters
48.5 in. a year: that's Pennington County's NOAA 1991-2020 snowfall normal, measured at RAPID CITY RGNL AP, SD US (11.8 mi away). See the density guide.
Before you rely on Pennington County's number
Treat the Pennington 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.)