Broadus, MT 59343 Frost Dates
59343, near Broadus, MT: the frost window
Typically, the last spring freeze lands around 05/16, roughly 261 days out. Fall's first freeze usually shows up around 09/28, roughly 135 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Broadus in Zone 4b (-25 to -20°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
Broadus's growing season runs out in roughly 4 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 05/16 isn't a guarantee
05/16 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/02 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/29 and only about 1 year in 10 sees frost after that.
Broadus against the rest of the dataset
Broadus's growing season runs about 135 days, ranking 37,910 of 40,283 US ZIP codes measured here, longest to shortest. Within MT, it ranks 102 of 392.
Learn more
Two guides worth reading on 59343: the frost range, on how to read the range around Broadus's dates instead of trusting one, and local microclimates, on what one yard in Broadus can differ from the 59343 normal.