Defiance, IA 51527 Frost Dates
51527, near Defiance, IA: the frost window
Typically, the last spring freeze lands around 04/27, roughly 242 days out. Fall's first freeze usually shows up around 10/09, roughly 165 days after the last spring frost.
Defiance 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
Defiance'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 04/27 isn't a guarantee
04/27 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/12 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/09 and only about 1 year in 10 sees frost after that.
Defiance against the rest of the dataset
At roughly 165 frost-free days, Defiance places 30,745 of 40,283 ZIP codes in this dataset. Within IA, it ranks 548 of 1,042.
Learn more
Two guides worth reading on 51527: local microclimates, on what one yard in Defiance can differ from the 51527 normal, and zone vs. frost date, on why Zone 5a and Defiance's frost date answer different questions.