St. Charles, MO 63346 Frost Dates
Frost dates for St. Charles, MO, ZIP 63346
Around 04/09 is the usual last spring frost, about 224 days away. The first fall frost typically arrives around 10/26, about 198 frost-free days later.
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.
What to do before the first frost
Zone 6b around St. Charles has about 8 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
Why 04/09 isn't a guarantee
04/09 is the middle of 30 years of NOAA records, not a promise. Plant by 03/27 and you're betting against frost in roughly 9 years out of 10. 04/25 is the safer bet, historically only a 1-in-10 chance of frost that late.
How St. Charles compares
About 198 days separate St. Charles's last and first frost, putting it 18,264 of 40,283 ZIP codes nationally. Within MO, it ranks 471 of 1,129.
Learn more
the frost range explains how to read the range around St. Charles's dates instead of trusting one, and local microclimates explains what one yard in St. Charles can differ from the 63346 normal.