Midwest, WY 82643 Frost Dates
Frost dates for Midwest, WY, ZIP 82643
Around 05/22 is the usual last spring frost, about 267 days away. The first fall frost typically arrives around 09/22, about 121 frost-free days later.
The USDA Plant Hardiness Zone Map puts Midwest in Zone 5a (-20 to -15°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
What to do before the first frost
Zone 5a around Midwest has about 4 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
Why 05/22 isn't a guarantee
05/22 is the middle of 30 years of NOAA records, not a promise. Plant by 05/08 and you're betting against frost in roughly 9 years out of 10. 06/06 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Midwest compares
At roughly 121 frost-free days, Midwest places 39,046 of 40,283 ZIP codes in this dataset. Within WY, it ranks 97 of 192.
Learn more
the frost range explains how to read the range around Midwest's dates instead of trusting one, and local microclimates explains what one yard in Midwest can differ from the 82643 normal.