Blairstown, IA 52209 Frost Dates
52209, near Blairstown, IA: the frost window
Typically, the last spring freeze lands around 04/28, roughly 243 days out. Fall's first freeze usually shows up around 10/10, roughly 165 days after the last spring frost.
Blairstown sits in USDA Zone 5a (-20 to -15°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
Blairstown'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.
How much risk comes with planting early here
04/28 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/14 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/11 and only about 1 year in 10 sees frost after that.
Blairstown against the rest of the dataset
Blairstown's growing season runs about 165 days, ranking 30,670 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 530 of 1,042.
Learn more
Two guides worth reading on 52209: local microclimates, on what one yard in Blairstown can differ from the 52209 normal, and zone vs. frost date, on why Zone 5a and Blairstown's frost date answer different questions.