Bozeman, MT 59719 Frost Dates
Frost dates for Bozeman, MT, ZIP 59719
The last spring frost here typically falls around 05/26, about 271 days from today. The first fall frost typically arrives around 09/22, about 116 frost-free days later.
Zone 5a (-20 to -15°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 Bozeman, not a forecast for this year.
What to do before the first frost
Zone 5a around Bozeman has about 4 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.
Why 05/26 isn't a guarantee
05/26 is the middle of 30 years of NOAA records, not a promise. Plant by 05/09 and you're betting against frost in roughly 9 years out of 10. 06/14 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Bozeman compares
About 116 days separate Bozeman's last and first frost, putting it 39,271 of 40,283 ZIP codes nationally. Within MT, it ranks 239 of 392.
Learn more
local microclimates explains what one yard in Bozeman can differ from the 59719 normal, and zone vs. frost date explains why Zone 5a and Bozeman's frost date answer different questions.