O'Fallon, MO Weather & Growing Conditions
Local forecast, frost dates, hardiness zone and planting guidance for O'Fallon, a city in St. Charles County, Missouri.
This Afternoon
58°F
Cloudy
Cloudy, with a high near 58. West wind around 7 mph.
7-day forecast for O'Fallon
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| This Afternoon | 58°F | Cloudy | 7 mph W | 0% |
| Tonight | 43°F | Partly Cloudy | 6 mph W | 0% |
| Thursday | 61°F | Mostly Sunny | 6 to 10 mph W | 9% |
| Thursday Night | 44°F | Isolated Rain Showers then Mostly Cloudy | 6 mph NW | 16% |
| Friday | 54°F | Partly Sunny | 6 to 9 mph N | 4% |
| Friday Night | 32°F | Mostly Clear | 1 to 5 mph N | 0% |
| Saturday | 53°F | Mostly Sunny | 2 mph N | 0% |
| Saturday Night | 32°F | Mostly Clear | 1 mph NW | 0% |
| Sunday | 60°F | Sunny | 3 mph W | 0% |
| Sunday Night | 35°F | Clear | 1 mph W | 0% |
| Monday | 65°F | Sunny | 3 mph SW | 0% |
| Monday Night | 39°F | Clear | 3 mph SW | 1% |
| Tuesday | 66°F | Sunny | 2 mph W | 3% |
| Tuesday Night | 40°F | Mostly Clear | 1 mph NW | 3% |
Forecast source: National Weather Service (api.weather.gov) for O'Fallon (38.785, -90.721). Updated through the day.
Growing snapshot for O'Fallon
Last spring frost
Apr 10
First fall frost
Oct 26
Growing season
199 days
Hardiness zone
6b
More local growing data for O'Fallon: nearby ZIP 63368 weather · frost dates · planting calendar · Missouri frost dates
Nearby towns & communities
Augusta
Cottleville
Dardenne Prairie
Defiance
Flint Hill
Foristell
Josephville
Lake St. Louis
New Melle
St. Paul
St. Peters
Weldon Spring
Weldon Spring Heights
Wentzville
West Alton
Climate data from the nearest NOAA station, Weldon Spring Nws, Mo (4.4 mi from O'Fallon). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 5, 2026.