Superior, WY 82902 Frost Dates
When can you plant in Superior, WY?
Typically, the last spring freeze lands around 05/22, roughly 267 days out. The first fall frost typically arrives around 09/28, about 126 frost-free days later.
Zone 5a (-20 to -15°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Superior, not a forecast for this year.
What to do before the first frost
About 4 weeks of growing season left in Superior before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 05/22 isn't a guarantee
05/22 is the middle of 30 years of NOAA records, not a promise. Plant by 05/05 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 Superior compares
Superior's growing season runs about 126 days, ranking 38,725 of 40,283 US ZIP codes measured here, longest to shortest. Within WY, it ranks 73 of 192.
Learn more
zone vs. frost date covers why Zone 5a and Superior's frost date answer different questions. the frost range covers how to read the range around Superior's dates instead of trusting one.