Irwin, IA 51446 Frost Dates
51446, near Irwin, IA: the frost window
The last spring frost here typically falls around 04/27, about 242 days from today. Fall's first freeze usually shows up around 10/09, roughly 165 days after the last spring frost.
Irwin 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
Irwin'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.
The actual range around Irwin's last frost
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.
Irwin against the rest of the dataset
About 165 days separate Irwin's last and first frost, putting it 30,732 of 40,283 ZIP codes nationally. Within IA, it ranks 545 of 1,042.
Learn more
Two guides worth reading on 51446: the frost range, on how to read the range around Irwin's dates instead of trusting one, and local microclimates, on what one yard in Irwin can differ from the 51446 normal.