Jefferson, IA 50129 Frost Dates
50129, near Jefferson, IA: the frost window
The last spring frost here typically falls around 04/26, about 241 days from today. Fall's first freeze usually shows up around 10/09, roughly 164 days after the last spring frost.
Zone 5b (-15 to -10°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Jefferson, not a forecast for this year.
Stretching the season past the first frost
Jefferson'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
04/26 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 05/08 and only about 1 year in 10 sees frost after that.
Jefferson against the rest of the dataset
At roughly 164 frost-free days, Jefferson places 30,926 of 40,283 ZIP codes in this dataset. Within IA, it ranks 582 of 1,042.
Learn more
Two guides worth reading on 50129: local microclimates, on what one yard in Jefferson can differ from the 50129 normal, and zone vs. frost date, on why Zone 5b and Jefferson's frost date answer different questions.