Miles City, MT 59338 Frost Dates
59338, near Miles City, MT: the frost window
Typically, the last spring freeze lands around 05/08, roughly 253 days out. Fall's first freeze usually shows up around 09/30, roughly 144 days after the last spring frost.
Miles City 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
Miles City'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 Miles City's last frost
05/08 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 05/21 and only about 1 year in 10 sees frost after that.
Miles City against the rest of the dataset
At roughly 144 frost-free days, Miles City places 36,355 of 40,283 ZIP codes in this dataset. Within MT, it ranks 38 of 392.
Learn more
Two guides worth reading on 59338: zone vs. frost date, on why Zone 4a and Miles City's frost date answer different questions, and the frost range, on how to read the range around Miles City's dates instead of trusting one.