Pinesdale, MT 59841 Frost Dates
59841, near Pinesdale, MT: the frost window
Typically, the last spring freeze lands around 05/23, roughly 268 days out. Fall's first freeze usually shows up around 09/21, roughly 118 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Pinesdale in Zone 5b (-15 to -10°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
Pinesdale's growing season runs out in roughly 3 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 05/23 isn't a guarantee
05/23 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/08 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/10 and only about 1 year in 10 sees frost after that.
Pinesdale against the rest of the dataset
About 118 days separate Pinesdale's last and first frost, putting it 39,215 of 40,283 ZIP codes nationally. Within MT, it ranks 229 of 392.
Learn more
Two guides worth reading on 59841: local microclimates, on what one yard in Pinesdale can differ from the 59841 normal, and zone vs. frost date, on why Zone 5b and Pinesdale's frost date answer different questions.