Deer Lodge, MT 59756 Frost Dates
59756, near Deer Lodge, MT: the frost window
Typically, the last spring freeze lands around 06/01, roughly 277 days out. Fall's first freeze usually shows up around 09/14, roughly 105 days after the last spring frost.
Zone 4b (-25 to -20°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 Deer Lodge, not a forecast for this year.
Stretching the season past the first frost
Deer Lodge's growing season runs out in roughly 2 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 06/01 isn't a guarantee
06/01 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 06/25 and only about 1 year in 10 sees frost after that.
Deer Lodge against the rest of the dataset
Deer Lodge's growing season runs about 105 days, ranking 39,599 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 293 of 392.
Learn more
Two guides worth reading on 59756: local microclimates, on what one yard in Deer Lodge can differ from the 59756 normal, and zone vs. frost date, on why Zone 4b and Deer Lodge's frost date answer different questions.