Rexburg, ID 83440 Frost Dates
83440, near Rexburg, ID: the frost window
Around 05/12 is the usual last spring frost, about 257 days away. Fall's first freeze usually shows up around 09/24, roughly 132 days after the last spring frost.
Zone 5a (-20 to -15°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 Rexburg, not a forecast for this year.
Stretching the season past the first frost
Rexburg'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 05/12 isn't a guarantee
05/12 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/29 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/02 and only about 1 year in 10 sees frost after that.
Rexburg against the rest of the dataset
Rexburg's growing season runs about 132 days, ranking 38,160 of 40,283 US ZIP codes measured here, longest to shortest. Within ID, it ranks 165 of 320.
Learn more
Two guides worth reading on 83440: zone vs. frost date, on why Zone 5a and Rexburg's frost date answer different questions, and the frost range, on how to read the range around Rexburg's dates instead of trusting one.