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.
Overnight
53°F
Chance Light Rain
A chance of rain before 1am, then a slight chance of drizzle between 1am and 4am. Mostly cloudy, with a low around 53. Southwest wind around 9 mph, with gusts as high as 22 mph. Chance of precipitation is 30%.
7-day forecast for O'Fallon
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 53°F | Chance Light Rain | 9 mph SW | 26% |
| Wednesday | 61°F | Mostly Cloudy | 7 to 14 mph W | 3% |
| Wednesday Night | 43°F | Partly Cloudy | 6 mph W | 0% |
| Thursday | 63°F | Sunny | 6 to 10 mph W | 4% |
| Thursday Night | 42°F | Mostly Cloudy | 6 mph NW | 9% |
| Friday | 57°F | Mostly Cloudy | 8 mph NW | 3% |
| Friday Night | 38°F | Mostly Cloudy | 1 to 5 mph N | 1% |
| Saturday | 56°F | Partly Sunny | 2 mph NW | 0% |
| Saturday Night | 35°F | Partly Cloudy | 2 mph W | 1% |
| Sunday | 62°F | Sunny | 2 to 6 mph W | 9% |
| Sunday Night | 36°F | Mostly Clear | 3 mph W | 3% |
| Monday | 66°F | Sunny | 6 mph SW | 2% |
| Monday Night | 40°F | Mostly Clear | 5 mph SW | 1% |
| Tuesday | 68°F | Sunny | 5 mph W | 1% |
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 4, 2026.