When to plant in Lake St. Louis, MO
USDA Zone 6bHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Lake St. Louis, Missouri — all computed from Lake St. Louis's nearest NOAA weather station.
In zone 6b, Lake St. Louis gardeners can grow many hardy perennials, while the last and first frost still dictate the annual vegetable calendar.
Frost probability
WELDON SPRING NWS · 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 Lake St. Louis’s own odds, recorded at WELDON SPRING NWS.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 6 | Apr 22 | Apr 8 | Oct 1 | Oct 16 | Oct 28 |
| 32°F | Apr 26 | Apr 10 | Mar 26 | Oct 12 | Oct 26 | Nov 8 |
| 28°F | Apr 15 | Mar 31 | Mar 12 | Oct 22 | Nov 5 | Nov 22 |
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 Lake St. Louis, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 18 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.
Lake St. Louis planting FAQ
When is the last spring frost in Lake St. Louis, MO?
Plan for the last spring frost in Lake St. Louis around April 10 (the date it has a 50% chance of a 32°F freeze). Anything frost-sensitive should go out after it.
When is the first fall frost in Lake St. Louis, MO?
In Lake St. Louis, the first 32°F freeze of fall lands around October 26 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Lake St. Louis in?
Lake St. Louis 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 Lake St. Louis?
Lake St. Louis has about 199 frost-free days — a moderate growing season — between the average last spring frost (April 10) and first fall frost (October 26).
When should I plant tomatoes in Lake St. Louis?
For Lake St. Louis, sow tomatoes indoors about February 13–February 27 and move the seedlings out around April 17, after the last spring frost.
Never miss a window in Lake St. Louis
An email when it’s time to start seeds, transplant, and sow — timed to Lake St. Louis’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- O'Fallon · 6 km
- Dardenne Prairie · 7 km
- Wentzville · 8 km
- St. Peters · 16 km
- Chesterfield · 23 km
- St. Charles · 23 km
- Wildwood · 25 km
- Troy · 26 km
Frost dates recorded at WELDON SPRING NWS, 13 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 Lake St. Louis, MO — Frost Dates & Zone 6b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00238805. Retrieved from https://blissgarden.com/missouri/lake-st-louis.