Ashton, ID 83420 Frost Dates
83420, near Ashton, ID: the frost window
Around 05/21 is the usual last spring frost, about 266 days away. Fall's first freeze usually shows up around 09/21, roughly 121 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Ashton in Zone 5a (-20 to -15°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
Ashton'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.
Why 05/21 isn't a guarantee
05/21 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/04 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/13 and only about 1 year in 10 sees frost after that.
Ashton against the rest of the dataset
At roughly 121 frost-free days, Ashton places 39,023 of 40,283 ZIP codes in this dataset. Within ID, it ranks 204 of 320.
Learn more
Two guides worth reading on 83420: the frost range, on how to read the range around Ashton's dates instead of trusting one, and local microclimates, on what one yard in Ashton can differ from the 83420 normal.