Missoula, MT 59847 Frost Dates
59847, near Missoula, MT: the frost window
Around 05/16 is the usual last spring frost, about 261 days away. Fall's first freeze usually shows up around 09/26, roughly 130 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Missoula 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
Missoula's growing season runs out in roughly 4 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Missoula's last frost
05/16 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/03 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/01 and only about 1 year in 10 sees frost after that.
Missoula against the rest of the dataset
About 130 days separate Missoula's last and first frost, putting it 38,350 of 40,283 ZIP codes nationally. Within MT, it ranks 129 of 392.
Learn more
Two guides worth reading on 59847: local microclimates, on what one yard in Missoula can differ from the 59847 normal, and zone vs. frost date, on why Zone 5b and Missoula's frost date answer different questions.