Chinook, MT 59523 Frost Dates
When can you plant in Chinook, MT?
Around 05/14 is the usual last spring frost, about 259 days away. The first fall frost typically arrives around 09/23, about 130 frost-free days later.
Zone 3b (-35 to -30°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Chinook, not a forecast for this year.
What to do before the first frost
About 4 weeks of growing season left in Chinook before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
The actual range around Chinook's last frost
05/14 is the middle of 30 years of NOAA records, not a promise. Plant by 05/01 and you're betting against frost in roughly 9 years out of 10. 05/27 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Chinook compares
At roughly 130 frost-free days, Chinook places 38,394 of 40,283 ZIP codes in this dataset. Within MT, it ranks 130 of 392.
Learn more
the frost range covers how to read the range around Chinook's dates instead of trusting one. local microclimates covers what one yard in Chinook can differ from the 59523 normal.