Grass Range, MT 59441 Frost Dates
Frost dates for Grass Range, MT, ZIP 59441
Around 05/19 is the usual last spring frost, about 264 days away. The first fall frost typically arrives around 09/25, about 128 frost-free days later.
Grass Range sits in USDA Zone 4b (-25 to -20°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 4b around Grass Range 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
05/19 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. 06/01 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Grass Range compares
About 128 days separate Grass Range's last and first frost, putting it 38,588 of 40,283 ZIP codes nationally. Within MT, it ranks 151 of 392.
Learn more
the frost range explains how to read the range around Grass Range's dates instead of trusting one, and local microclimates explains what one yard in Grass Range can differ from the 59441 normal.