Lake Mills, IA 50450 Frost Dates
50450, near Lake Mills, IA: the frost window
Around 05/04 is the usual last spring frost, about 249 days away. Fall's first freeze usually shows up around 10/04, roughly 152 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Lake Mills 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
Lake Mills's growing season runs out in roughly 5 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
05/04 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/21 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/16 and only about 1 year in 10 sees frost after that.
Lake Mills against the rest of the dataset
Lake Mills's growing season runs about 152 days, ranking 34,780 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 947 of 1,042.
Learn more
Two guides worth reading on 50450: local microclimates, on what one yard in Lake Mills can differ from the 50450 normal, and zone vs. frost date, on why Zone 5a and Lake Mills's frost date answer different questions.