Opheim, MT 59244 Frost Dates
59244, near Opheim, MT: the frost window
Typically, the last spring freeze lands around 06/05, roughly 281 days out. Fall's first freeze usually shows up around 09/02, roughly 89 days after the last spring frost.
Opheim 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
Opheim's growing season runs out in roughly 1 week — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 06/05 isn't a guarantee
06/05 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/22 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/23 and only about 1 year in 10 sees frost after that.
Opheim against the rest of the dataset
Opheim's growing season runs about 89 days, ranking 39,937 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 341 of 392.
Learn more
Two guides worth reading on 59244: zone vs. frost date, on why Zone 3b and Opheim's frost date answer different questions, and the frost range, on how to read the range around Opheim's dates instead of trusting one.