Osage, IA 50461 Frost Dates
50461, near Osage, IA: the frost window
Around 04/30 is the usual last spring frost, about 245 days away. Fall's first freeze usually shows up around 10/09, roughly 163 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Osage 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
Osage'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 04/14 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.
Osage against the rest of the dataset
At roughly 163 frost-free days, Osage places 31,389 of 40,283 ZIP codes in this dataset. Within IA, it ranks 662 of 1,042.
Learn more
Two guides worth reading on 50461: local microclimates, on what one yard in Osage can differ from the 50461 normal, and zone vs. frost date, on why Zone 5a and Osage's frost date answer different questions.