Harlem, MT 59542 Frost Dates
59542, near Harlem, MT: the frost window
Typically, the last spring freeze lands around 05/19, roughly 264 days out. Fall's first freeze usually shows up around 09/21, roughly 124 days after the last spring frost.
Harlem 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
Harlem'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 Harlem's last frost
05/19 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/07 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/01 and only about 1 year in 10 sees frost after that.
Harlem against the rest of the dataset
About 124 days separate Harlem's last and first frost, putting it 38,856 of 40,283 ZIP codes nationally. Within MT, it ranks 188 of 392.
Learn more
Two guides worth reading on 59542: the frost range, on how to read the range around Harlem's dates instead of trusting one, and local microclimates, on what one yard in Harlem can differ from the 59542 normal.