Rock Springs, WY 82943 Frost Dates
When can you plant in Rock Springs, WY?
Typically, the last spring freeze lands around 05/24, roughly 269 days out. The first fall frost typically arrives around 09/24, about 121 frost-free days later.
Rock Springs sits in USDA Zone 5a (-20 to -15°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
About 4 weeks of growing season left in Rock Springs before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 05/24 isn't a guarantee
05/24 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. 06/09 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Rock Springs compares
About 121 days separate Rock Springs's last and first frost, putting it 38,990 of 40,283 ZIP codes nationally. Within WY, it ranks 92 of 192.
Learn more
local microclimates covers what one yard in Rock Springs can differ from the 82943 normal. zone vs. frost date covers why Zone 5a and Rock Springs's frost date answer different questions.