Cascade, MT 59421 Frost Dates
When can you plant in Cascade, MT?
Typically, the last spring freeze lands around 05/21, roughly 266 days out. The first fall frost typically arrives around 09/19, about 120 frost-free days later.
The USDA Plant Hardiness Zone Map puts Cascade in Zone 4b (-25 to -20°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
What to do before the first frost
About 3 weeks of growing season left in Cascade before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 05/21 isn't a guarantee
05/21 is the middle of 30 years of NOAA records, not a promise. Plant by 05/05 and you're betting against frost in roughly 9 years out of 10. 06/06 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Cascade compares
Cascade's growing season runs about 120 days, ranking 39,093 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 218 of 392.
Learn more
local microclimates covers what one yard in Cascade can differ from the 59421 normal. zone vs. frost date covers why Zone 4b and Cascade's frost date answer different questions.