Columbia Falls, MT 59936 Frost Dates
Frost dates for Columbia Falls, MT, ZIP 59936
Typically, the last spring freeze lands around 05/18, roughly 263 days out. The first fall frost typically arrives around 09/20, about 124 frost-free days later.
Zone 5a (-20 to -15°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 Columbia Falls, not a forecast for this year.
What to do before the first frost
Zone 5a around Columbia Falls 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.
Why 05/18 isn't a guarantee
05/18 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. 06/04 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Columbia Falls compares
At roughly 124 frost-free days, Columbia Falls places 38,832 of 40,283 ZIP codes in this dataset. Within MT, it ranks 183 of 392.
Learn more
the frost range explains how to read the range around Columbia Falls's dates instead of trusting one, and local microclimates explains what one yard in Columbia Falls can differ from the 59936 normal.