Colstrip, MT 59312 Frost Dates
Colstrip, MT: when does the frost end?
Around 05/26 is the usual last spring frost, about 271 days away. Fall's first freeze usually shows up around 09/16, roughly 111 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Colstrip in Zone 4a (-30 to -25°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
With roughly 3 weeks until Colstrip's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
The actual range around Colstrip's last frost
05/26 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/12 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/13 and only about 1 year in 10 sees frost after that.
Colstrip against the rest of the dataset
About 111 days separate Colstrip's last and first frost, putting it 39,461 of 40,283 ZIP codes nationally. Within MT, it ranks 271 of 392.
Learn more
Before leaning on 59312's figures: zone vs. frost date explains why Zone 4a and Colstrip's frost date answer different questions, while the frost range explains how to read the range around Colstrip's dates instead of trusting one.