Billings, MT 59105 Frost Dates
59105, near Billings, MT: the frost window
The last spring frost here typically falls around 05/04, about 249 days from today. Fall's first freeze usually shows up around 10/07, roughly 156 days after the last spring frost.
Zone 5a (-20 to -15°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Billings, not a forecast for this year.
Stretching the season past the first frost
Billings's growing season runs out in roughly 6 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 05/04 isn't a guarantee
05/04 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/20 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/18 and only about 1 year in 10 sees frost after that.
Billings against the rest of the dataset
Billings's growing season runs about 156 days, ranking 33,489 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 11 of 392.
Learn more
Two guides worth reading on 59105: local microclimates, on what one yard in Billings can differ from the 59105 normal, and zone vs. frost date, on why Zone 5a and Billings's frost date answer different questions.