Missoula, MT 59804 Frost Dates
When can you plant in Missoula, MT?
The last spring frost here typically falls around 05/16, about 261 days from today. The first fall frost typically arrives around 09/26, about 130 frost-free days later.
Zone 5b (-15 to -10°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 Missoula, not a forecast for this year.
What to do before the first frost
About 4 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.
The actual range around Missoula's last frost
05/16 is the middle of 30 years of NOAA records, not a promise. Plant by 05/03 and you're betting against frost in roughly 9 years out of 10. 06/01 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Missoula compares
About 130 days separate Missoula's last and first frost, putting it 38,349 of 40,283 ZIP codes nationally. Within MT, it ranks 128 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.