Kirby, WY 82430 Frost Dates
When can you plant in Kirby, WY?
The last spring frost here typically falls around 05/24, about 269 days from today. The first fall frost typically arrives around 09/16, about 112 frost-free days later.
Kirby sits in USDA Zone 4b (-25 to -20°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 3 weeks of growing season left in Kirby 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 05/12 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 Kirby compares
Kirby's growing season runs about 112 days, ranking 39,448 of 40,283 US ZIP codes measured here, longest to shortest. Within WY, it ranks 127 of 192.
Learn more
zone vs. frost date covers why Zone 4b and Kirby's frost date answer different questions. the frost range covers how to read the range around Kirby's dates instead of trusting one.