Circle, MT 59214 Frost Dates
Frost dates for Circle, MT, ZIP 59214
Typically, the last spring freeze lands around 05/20, roughly 265 days out. The first fall frost typically arrives around 09/19, about 121 frost-free days later.
Circle 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
Zone 4a around Circle has about 3 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
The actual range around Circle's last frost
05/20 is the middle of 30 years of NOAA records, not a promise. Plant by 05/06 and you're betting against frost in roughly 9 years out of 10. 06/05 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Circle compares
About 121 days separate Circle's last and first frost, putting it 39,035 of 40,283 ZIP codes nationally. Within MT, it ranks 209 of 392.
Learn more
the frost range explains how to read the range around Circle's dates instead of trusting one, and local microclimates explains what one yard in Circle can differ from the 59214 normal.