Circle, MT 59339 Frost Dates
When can you plant in Circle, MT?
The last spring frost here typically falls around 05/26, about 271 days from today. The first fall frost typically arrives around 09/17, about 113 frost-free days later.
The USDA Plant Hardiness Zone Map puts Circle 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 Circle before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
The actual range around Circle's last frost
05/26 is the middle of 30 years of NOAA records, not a promise. Plant by 05/13 and you're betting against frost in roughly 9 years out of 10. 06/13 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Circle compares
At roughly 113 frost-free days, Circle places 39,403 of 40,283 ZIP codes in this dataset. Within MT, it ranks 260 of 392.
Learn more
the frost range covers how to read the range around Circle's dates instead of trusting one. local microclimates covers what one yard in Circle can differ from the 59339 normal.