Coralville, IA 52241 Frost Dates
52241, near Coralville, IA: the frost window
Around 04/21 is the usual last spring frost, about 236 days away. Fall's first freeze usually shows up around 10/18, roughly 180 days after the last spring frost.
Coralville sits in USDA Zone 5b (-15 to -10°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
Coralville's growing season runs out in roughly 7 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 04/21 isn't a guarantee
04/21 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/05 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/06 and only about 1 year in 10 sees frost after that.
Coralville against the rest of the dataset
At roughly 180 frost-free days, Coralville places 24,798 of 40,283 ZIP codes in this dataset. Within IA, it ranks 89 of 1,042.
Learn more
Two guides worth reading on 52241: local microclimates, on what one yard in Coralville can differ from the 52241 normal, and zone vs. frost date, on why Zone 5b and Coralville's frost date answer different questions.