Havre, MT 59501 Frost Dates
Havre, MT: when does the frost end?
Around 05/15 is the usual last spring frost, about 260 days away. Fall's first freeze usually shows up around 09/23, roughly 129 days after the last spring frost.
Havre sits in USDA Zone 3b (-35 to -30°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 Havre's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/15 isn't a guarantee
05/15 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/03 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/27 and only about 1 year in 10 sees frost after that.
Havre against the rest of the dataset
About 129 days separate Havre's last and first frost, putting it 38,447 of 40,283 ZIP codes nationally. Within MT, it ranks 134 of 392.
Learn more
Before leaning on 59501's figures: zone vs. frost date explains why Zone 3b and Havre's frost date answer different questions, while the frost range explains how to read the range around Havre's dates instead of trusting one.