Clarion, IA 50525 Frost Dates
50525, near Clarion, IA: the frost window
Typically, the last spring freeze lands around 04/30, roughly 245 days out. Fall's first freeze usually shows up around 10/10, roughly 162 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Clarion 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
Clarion's growing season runs out in roughly 6 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 04/30 isn't a guarantee
04/30 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/17 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/12 and only about 1 year in 10 sees frost after that.
Clarion against the rest of the dataset
At roughly 162 frost-free days, Clarion places 31,746 of 40,283 ZIP codes in this dataset. Within IA, it ranks 695 of 1,042.
Learn more
Two guides worth reading on 50525: local microclimates, on what one yard in Clarion can differ from the 50525 normal, and zone vs. frost date, on why Zone 5a and Clarion's frost date answer different questions.