White Sulphur Springs, MT 59645 Frost Dates
Frost dates for White Sulphur Springs, MT, ZIP 59645
Typically, the last spring freeze lands around 06/04, roughly 280 days out. The first fall frost typically arrives around 09/11, about 97 frost-free days later.
White Sulphur Springs 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 White Sulphur Springs has about 2 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 White Sulphur Springs's last frost
06/04 is the middle of 30 years of NOAA records, not a promise. Plant by 05/21 and you're betting against frost in roughly 9 years out of 10. 06/20 is the safer bet, historically only a 1-in-10 chance of frost that late.
How White Sulphur Springs compares
About 97 days separate White Sulphur Springs's last and first frost, putting it 39,778 of 40,283 ZIP codes nationally. Within MT, it ranks 322 of 392.
Learn more
local microclimates explains what one yard in White Sulphur Springs can differ from the 59645 normal, and zone vs. frost date explains why Zone 4b and White Sulphur Springs's frost date answer different questions.