Rock River, WY 82051 Frost Dates
When can you plant in Rock River, WY?
The last spring frost here typically falls around 05/22, about 267 days from today. The first fall frost typically arrives around 09/24, about 125 frost-free days later.
Rock River sits in USDA Zone 4a (-30 to -25°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 River before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
How much risk comes with planting early here
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. 06/05 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Rock River compares
At roughly 125 frost-free days, Rock River places 38,813 of 40,283 ZIP codes in this dataset. Within WY, it ranks 80 of 192.
Learn more
local microclimates covers what one yard in Rock River can differ from the 82051 normal. zone vs. frost date covers why Zone 4a and Rock River's frost date answer different questions.