St. Charles, MO 63338 Frost Dates
St. Charles, MO: when does the frost end?
Typically, the last spring freeze lands around 04/09, roughly 224 days out. Fall's first freeze usually shows up around 10/26, roughly 198 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts St. Charles in Zone 6b (-5 to 0°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
With roughly 8 weeks until St. Charles's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
The actual range around St. Charles's last frost
04/09 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/27 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/25 and only about 1 year in 10 sees frost after that.
St. Charles against the rest of the dataset
About 198 days separate St. Charles's last and first frost, putting it 18,263 of 40,283 ZIP codes nationally. Within MO, it ranks 470 of 1,129.
Learn more
Before leaning on 63338's figures: local microclimates explains what one yard in St. Charles can differ from the 63338 normal, while zone vs. frost date explains why Zone 6b and St. Charles's frost date answer different questions.