Roundup, MT 59073 Frost Dates
When can you plant in Roundup, MT?
Typically, the last spring freeze lands around 05/20, roughly 265 days out. The first fall frost typically arrives around 09/21, about 124 frost-free days later.
Roundup sits in USDA Zone 4b (-25 to -20°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 3 weeks of growing season left in Roundup before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
The actual range around Roundup'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. 06/02 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Roundup compares
About 124 days separate Roundup's last and first frost, putting it 38,843 of 40,283 ZIP codes nationally. Within MT, it ranks 185 of 392.
Learn more
the frost range covers how to read the range around Roundup's dates instead of trusting one. local microclimates covers what one yard in Roundup can differ from the 59073 normal.