Mullan, ID 83846 Frost Dates
83846, near Mullan, ID: the frost window
Typically, the last spring freeze lands around 05/12, roughly 257 days out. Fall's first freeze usually shows up around 09/30, roughly 138 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Mullan in Zone 6a (-10 to -5°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
Mullan's growing season runs out in roughly 5 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 05/12 isn't a guarantee
05/12 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/26 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/19 and only about 1 year in 10 sees frost after that.
Mullan against the rest of the dataset
Mullan's growing season runs about 138 days, ranking 37,434 of 40,283 US ZIP codes measured here, longest to shortest. Within ID, it ranks 154 of 320.
Learn more
Two guides worth reading on 83846: local microclimates, on what one yard in Mullan can differ from the 83846 normal, and zone vs. frost date, on why Zone 6a and Mullan's frost date answer different questions.