Culbertson, MT 59218 Frost Dates
59218, near Culbertson, MT: the frost window
The last spring frost here typically falls around 05/21, about 266 days from today. Fall's first freeze usually shows up around 09/20, roughly 120 days after the last spring frost.
Culbertson 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.
Stretching the season past the first frost
Culbertson's growing season runs out in roughly 3 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Culbertson's last frost
05/21 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/08 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/03 and only about 1 year in 10 sees frost after that.
Culbertson against the rest of the dataset
About 120 days separate Culbertson's last and first frost, putting it 39,088 of 40,283 ZIP codes nationally. Within MT, it ranks 217 of 392.
Learn more
Two guides worth reading on 59218: the frost range, on how to read the range around Culbertson's dates instead of trusting one, and local microclimates, on what one yard in Culbertson can differ from the 59218 normal.