Dedham, IA 51440 Frost Dates
51440, near Dedham, IA: the frost window
Typically, the last spring freeze lands around 04/26, roughly 241 days out. Fall's first freeze usually shows up around 10/09, roughly 164 days after the last spring frost.
Zone 5a (-20 to -15°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 Dedham, not a forecast for this year.
Stretching the season past the first frost
Dedham'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.
Dedham against the rest of the dataset
Dedham's growing season runs about 164 days, ranking 31,207 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 632 of 1,042.
Learn more
Two guides worth reading on 51440: zone vs. frost date, on why Zone 5a and Dedham's frost date answer different questions, and the frost range, on how to read the range around Dedham's dates instead of trusting one.