Stevensville, MT 59870 Frost Dates
Frost dates for Stevensville, MT, ZIP 59870
The last spring frost here typically falls around 05/22, about 267 days from today. The first fall frost typically arrives around 09/19, about 115 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 Stevensville, not a forecast for this year.
What to do before the first frost
Zone 5b around Stevensville has about 3 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
The actual range around Stevensville's last frost
05/22 is the middle of 30 years of NOAA records, not a promise. Plant by 05/07 and you're betting against frost in roughly 9 years out of 10. 06/13 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Stevensville compares
About 115 days separate Stevensville's last and first frost, putting it 39,315 of 40,283 ZIP codes nationally. Within MT, it ranks 247 of 392.
Learn more
local microclimates explains what one yard in Stevensville can differ from the 59870 normal, and zone vs. frost date explains why Zone 5b and Stevensville's frost date answer different questions.