Cowley, WY 82420 Frost Dates
Cowley, WY: when does the frost end?
Typically, the last spring freeze lands around 05/09, roughly 254 days out. Fall's first freeze usually shows up around 09/29, roughly 142 days after the last spring frost.
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 Cowley, not a forecast for this year.
Stretching the season past the first frost
With roughly 5 weeks until Cowley's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/09 isn't a guarantee
05/09 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/27 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/25 and only about 1 year in 10 sees frost after that.
Cowley against the rest of the dataset
Cowley's growing season runs about 142 days, ranking 36,772 of 40,283 US ZIP codes measured here, longest to shortest. Within WY, it ranks 20 of 192.
Learn more
Before leaning on 82420's figures: the frost range explains how to read the range around Cowley's dates instead of trusting one, while local microclimates explains what one yard in Cowley can differ from the 82420 normal.