Butte-Silver Bow, MT 59702 Frost Dates
Butte-Silver Bow, MT: when does the frost end?
Typically, the last spring freeze lands around 06/13, roughly 289 days out. Fall's first freeze usually shows up around 09/05, roughly 83 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Butte-Silver Bow in Zone 4a (-30 to -25°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
With roughly 1 week until Butte-Silver Bow's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 06/13 isn't a guarantee
06/13 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/27 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 07/01 and only about 1 year in 10 sees frost after that.
Butte-Silver Bow against the rest of the dataset
At roughly 83 frost-free days, Butte-Silver Bow places 40,011 of 40,283 ZIP codes in this dataset. Within MT, it ranks 352 of 392.
Learn more
Before leaning on 59702's figures: zone vs. frost date explains why Zone 4a and Butte-Silver Bow's frost date answer different questions, while the frost range explains how to read the range around Butte-Silver Bow's dates instead of trusting one.