Harlem, MT 59526 Frost Dates
Harlem, MT: when does the frost end?
Around 05/16 is the usual last spring frost, about 261 days away. Fall's first freeze usually shows up around 09/22, roughly 128 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
With roughly 4 weeks until Harlem's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/16 isn't a guarantee
05/16 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/06 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/28 and only about 1 year in 10 sees frost after that.
Harlem against the rest of the dataset
About 128 days separate Harlem's last and first frost, putting it 38,565 of 40,283 ZIP codes nationally. Within MT, it ranks 148 of 392.
Learn more
Before leaning on 59526's figures: zone vs. frost date explains why Zone 4a and Harlem's frost date answer different questions, while the frost range explains how to read the range around Harlem's dates instead of trusting one.