Dillon, MT 59724 Frost Dates
When can you plant in Dillon, MT?
Typically, the last spring freeze lands around 06/05, roughly 281 days out. The first fall frost typically arrives around 09/13, about 98 frost-free days later.
Dillon 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
About 2 weeks of growing season left in Dillon before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 06/05 isn't a guarantee
06/05 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. 06/23 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Dillon compares
Dillon's growing season runs about 98 days, ranking 39,755 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 319 of 392.
Learn more
the frost range covers how to read the range around Dillon's dates instead of trusting one. local microclimates covers what one yard in Dillon can differ from the 59724 normal.