Fromberg, MT 59066 Frost Dates
Fromberg, MT: when does the frost end?
Around 05/14 is the usual last spring frost, about 259 days away. Fall's first freeze usually shows up around 09/24, roughly 129 days after the last spring frost.
Fromberg sits in USDA Zone 5a (-20 to -15°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 Fromberg's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
The actual range around Fromberg's last frost
05/14 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/02 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/30 and only about 1 year in 10 sees frost after that.
Fromberg against the rest of the dataset
About 129 days separate Fromberg's last and first frost, putting it 38,491 of 40,283 ZIP codes nationally. Within MT, it ranks 143 of 392.
Learn more
Before leaning on 59066's figures: local microclimates explains what one yard in Fromberg can differ from the 59066 normal, while zone vs. frost date explains why Zone 5a and Fromberg's frost date answer different questions.