Cascade, MT 59485 Frost Dates
Frost dates for Cascade, MT, ZIP 59485
Typically, the last spring freeze lands around 06/02, roughly 278 days out. The first fall frost typically arrives around 09/10, about 96 frost-free days later.
Zone 4a (-30 to -25°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 Cascade, not a forecast for this year.
What to do before the first frost
Zone 4a around Cascade 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.
Why 06/02 isn't a guarantee
06/02 is the middle of 30 years of NOAA records, not a promise. Plant by 05/18 and you're betting against frost in roughly 9 years out of 10. 06/21 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Cascade compares
Cascade's growing season runs about 96 days, ranking 39,801 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 327 of 392.
Learn more
the frost range explains how to read the range around Cascade's dates instead of trusting one, and local microclimates explains what one yard in Cascade can differ from the 59485 normal.