St. Charles, IA 50240 Frost Dates
St. Charles, IA: when does the frost end?
The last spring frost here typically falls around 04/24, about 239 days from today. Fall's first freeze usually shows up around 10/12, roughly 168 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 St. Charles, not a forecast for this year.
Stretching the season past the first frost
With roughly 6 weeks until St. Charles's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 04/24 isn't a guarantee
04/24 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/11 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.
St. Charles against the rest of the dataset
St. Charles's growing season runs about 168 days, ranking 29,757 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 383 of 1,042.
Learn more
Before leaning on 50240's figures: local microclimates explains what one yard in St. Charles can differ from the 50240 normal, while zone vs. frost date explains why Zone 5b and St. Charles's frost date answer different questions.