When to plant in St. Charles, MO
USDA Zone 6bEverything below — frost dates, hardiness zone, and what to plant when in St. Charles, Missouri — is derived from the closest NOAA station with complete climate normals.
Zone 6b means St. Charles sees real winter cold, but a good range of perennials survive; the frost dates above govern when annual vegetables go out.
The average first fall frost in St. Charles is now 5 days later than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
ST CHARLES ELM PT · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are St. Charles’s own odds, recorded at ST CHARLES ELM PT.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 5 | Apr 21 | Apr 5 | Oct 7 | Oct 19 | Oct 31 |
| 32°F | Apr 24 | Apr 8 | Mar 23 | Oct 16 | Oct 29 | Nov 12 |
| 28°F | Apr 15 | Mar 30 | Mar 9 | Oct 29 | Nov 10 | Nov 28 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in St. Charles, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 12 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
St. Charles planting FAQ
When is the last spring frost in St. Charles, MO?
St. Charles's average last spring frost falls near April 8 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in St. Charles, MO?
The first fall frost in St. Charles typically arrives around October 29 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is St. Charles in?
St. Charles is in USDA hardiness zone 6b. In zone 6b, winters are moderate — most common vegetables grow well in season.
How long is the growing season in St. Charles?
There are roughly 204 frost-free days in St. Charles (a moderate growing season), running from the average last frost around April 8 to the first fall frost near October 29.
When should I plant tomatoes in St. Charles?
In St. Charles, start tomato seeds indoors around February 11–February 25, then transplant seedlings outdoors around April 15 once the danger of frost has passed.
Never miss a window in St. Charles
An email when it’s time to start seeds, transplant, and sow — timed to St. Charles’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- St. Peters · 8 km
- Bridgeton · 9 km
- Maryland Heights · 10 km
- Hazelwood · 10 km
- St. Ann · 14 km
- Creve Coeur · 16 km
- Chesterfield · 16 km
- Florissant · 16 km
Frost dates recorded at ST CHARLES ELM PT, 2 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in St. Charles, MO — Frost Dates & Zone 6b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00237397. Retrieved from https://blissgarden.com/missouri/st-charles.