Troy, MT 59935 Frost Dates
When can you plant in Troy, MT?
Typically, the last spring freeze lands around 05/14, roughly 259 days out. The first fall frost typically arrives around 09/25, about 132 frost-free days later.
The USDA Plant Hardiness Zone Map puts Troy in Zone 6a (-10 to -5°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 4 weeks of growing season left in Troy before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 05/14 isn't a guarantee
05/14 is the middle of 30 years of NOAA records, not a promise. Plant by 04/29 and you're betting against frost in roughly 9 years out of 10. 05/31 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Troy compares
Troy's growing season runs about 132 days, ranking 38,210 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 123 of 392.
Learn more
zone vs. frost date covers why Zone 6a and Troy's frost date answer different questions. the frost range covers how to read the range around Troy's dates instead of trusting one.