Missoula, MT 59808 Frost Dates
When can you plant in Missoula, MT?
Typically, the last spring freeze lands around 05/06, roughly 251 days out. The first fall frost typically arrives around 10/04, about 151 frost-free days later.
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.
What to do before the first frost
About 5 weeks of growing season left in Missoula before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
How much risk comes with planting early here
05/06 is the middle of 30 years of NOAA records, not a promise. Plant by 04/24 and you're betting against frost in roughly 9 years out of 10. 05/19 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Missoula compares
Missoula's growing season runs about 151 days, ranking 34,939 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 14 of 392.
Learn more
zone vs. frost date covers why Zone 5b and Missoula's frost date answer different questions. the frost range covers how to read the range around Missoula's dates instead of trusting one.