Great Falls, MT 59487 Frost Dates
When can you plant in Great Falls, MT?
The last spring frost here typically falls around 06/02, about 278 days from today. The first fall frost typically arrives around 09/10, about 96 frost-free days later.
Great Falls sits in USDA Zone 4a (-30 to -25°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 Great Falls before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
The actual range around Great Falls's last frost
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 Great Falls compares
Great Falls's growing season runs about 96 days, ranking 39,788 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 323 of 392.
Learn more
local microclimates covers what one yard in Great Falls can differ from the 59487 normal. zone vs. frost date covers why Zone 4a and Great Falls's frost date answer different questions.