SnowLoadCheck

Madison County, IL Roof Snow Load - 20 psf

What ASCE 7 says about snow load in Madison County

Moderate
20 psf

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. §7.3.4's low-slope minimum of 20 psf is what actually governs on a flat or low-pitch roof here - higher than the 14 psf the base ground-load formula gives.

Converted to something you can actually eyeball on a roof: about 44 in. of fresh powder, 16 in. once it settles and packs down, or just 4 in. if it's turned to ice. Modern-code homes carry a load like this without issue; an older addition, a carport, or any flat-roofed section is where it is worth checking first.

Madison County in numbers

Where Madison County's figure sits nationally

Out of 2,758 rated US counties, Madison County sits at #571, the top 21% nationally - #8 of 102 within Illinois. 19.3 psf is Illinois's typical county figure - Madison County beats it by 0.7 psf.

Near 38.8271°N 89.9002°W, FIPS 17119: Madison County counts 263,017 residents and a 20 psf map value, which the code's own factors turn into 20 psf.

How much it actually snows in Madison County

Most winters bring Madison County roughly 10.8 in. of snow - NOAA's normal at EDWARDSVILLE 2 W, IL US, 5.7 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.)