Diagonal, IA 50845 Frost Dates
50845, near Diagonal, IA: the frost window
Typically, the last spring freeze lands around 04/25, roughly 240 days out. Fall's first freeze usually shows up around 10/12, roughly 169 days after the last spring frost.
Diagonal sits in USDA Zone 5b (-15 to -10°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
Diagonal'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 04/25 isn't a guarantee
04/25 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/10 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.
Diagonal against the rest of the dataset
Diagonal's growing season runs about 169 days, ranking 29,590 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 347 of 1,042.
Learn more
Two guides worth reading on 50845: zone vs. frost date, on why Zone 5b and Diagonal's frost date answer different questions, and the frost range, on how to read the range around Diagonal's dates instead of trusting one.