Joliet, MT 59041 Frost Dates
59041, near Joliet, MT: the frost window
Around 05/29 is the usual last spring frost, about 274 days away. Fall's first freeze usually shows up around 09/15, roughly 107 days after the last spring frost.
Joliet 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
Joliet's growing season runs out in roughly 3 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 Joliet's last frost
05/29 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/14 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/17 and only about 1 year in 10 sees frost after that.
Joliet against the rest of the dataset
About 107 days separate Joliet's last and first frost, putting it 39,568 of 40,283 ZIP codes nationally. Within MT, it ranks 286 of 392.
Learn more
Two guides worth reading on 59041: zone vs. frost date, on why Zone 5a and Joliet's frost date answer different questions, and the frost range, on how to read the range around Joliet's dates instead of trusting one.