Butte-Silver Bow, MT 59727 Frost Dates
Frost dates for Butte-Silver Bow, MT, ZIP 59727
Typically, the last spring freeze lands around 06/10, roughly 286 days out. The first fall frost typically arrives around 09/07, about 85 frost-free days later.
Butte-Silver Bow 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 Butte-Silver Bow has about 1 week 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 06/10 isn't a guarantee
06/10 is the middle of 30 years of NOAA records, not a promise. Plant by 05/23 and you're betting against frost in roughly 9 years out of 10. 07/02 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Butte-Silver Bow compares
Butte-Silver Bow's growing season runs about 85 days, ranking 39,981 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 351 of 392.
Learn more
the frost range explains how to read the range around Butte-Silver Bow's dates instead of trusting one, and local microclimates explains what one yard in Butte-Silver Bow can differ from the 59727 normal.