Fromberg, MT 59029 Frost Dates
Frost dates for Fromberg, MT, ZIP 59029
Around 05/14 is the usual last spring frost, about 259 days away. The first fall frost typically arrives around 09/24, about 129 frost-free days later.
Fromberg sits in USDA Zone 5a (-20 to -15°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
Zone 5a around Fromberg 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.
How much risk comes with planting early here
05/14 is the middle of 30 years of NOAA records, not a promise. Plant by 05/02 and you're betting against frost in roughly 9 years out of 10. 05/30 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Fromberg compares
At roughly 129 frost-free days, Fromberg places 38,490 of 40,283 ZIP codes in this dataset. Within MT, it ranks 142 of 392.
Learn more
local microclimates explains what one yard in Fromberg can differ from the 59029 normal, and zone vs. frost date explains why Zone 5a and Fromberg's frost date answer different questions.