Billings, MT 59101 Frost Dates
59101, near Billings, MT: the frost window
Around 05/10 is the usual last spring frost, about 255 days away. Fall's first freeze usually shows up around 10/01, roughly 142 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Billings in Zone 5a (-20 to -15°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
Billings's growing season runs out in roughly 5 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 Billings's last frost
05/10 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/26 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/24 and only about 1 year in 10 sees frost after that.
Billings against the rest of the dataset
About 142 days separate Billings's last and first frost, putting it 36,695 of 40,283 ZIP codes nationally. Within MT, it ranks 46 of 392.
Learn more
Two guides worth reading on 59101: local microclimates, on what one yard in Billings can differ from the 59101 normal, and zone vs. frost date, on why Zone 5a and Billings's frost date answer different questions.