St. Charles, ID 83272 Frost Dates
83272, near St. Charles, ID: the frost window
The last spring frost here typically falls around 05/15, about 260 days from today. Fall's first freeze usually shows up around 10/04, roughly 140 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts St. Charles 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
St. Charles'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 05/15 isn't a guarantee
05/15 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/30 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/05 and only about 1 year in 10 sees frost after that.
St. Charles against the rest of the dataset
St. Charles's growing season runs about 140 days, ranking 37,178 of 40,283 US ZIP codes measured here, longest to shortest. Within ID, it ranks 152 of 320.
Learn more
Two guides worth reading on 83272: local microclimates, on what one yard in St. Charles can differ from the 83272 normal, and zone vs. frost date, on why Zone 5a and St. Charles's frost date answer different questions.