O'Fallon, MO Weather & Growing Conditions
Overnight
52°F
Slight Chance Drizzle
A slight chance of drizzle before 4am. Mostly cloudy, with a low around 52. Southwest wind around 9 mph, with gusts as high as 21 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Overnight | 52°F | Slight Chance Drizzle | 9 mph SW | 13% |
| Wednesday | 61°F | Mostly Cloudy | 7 to 14 mph W | 2% |
| Wednesday Night | 41°F | Partly Cloudy | 6 mph W | 0% |
| Thursday | 63°F | Sunny | 6 to 10 mph W | 0% |
| Thursday Night | 43°F | Mostly Cloudy | 6 mph NW | 3% |
| Friday | 56°F | Partly Sunny | 6 to 10 mph N | 5% |
| Friday Night | 34°F | Partly Cloudy | 1 to 5 mph N | 0% |
| Saturday | 55°F | Mostly Sunny | 0 to 3 mph N | 0% |
| Saturday Night | 33°F | Partly Cloudy | 2 mph NW | 0% |
| Sunday | 60°F | Sunny | 5 mph NW | 1% |
| Sunday Night | 34°F | Clear | 1 mph W | 0% |
| Monday | 66°F | Sunny | 1 to 5 mph SW | 0% |
| Monday Night | 39°F | Clear | 3 mph SW | 1% |
| Tuesday | 68°F | Sunny | 3 mph W | 1% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for O'Fallon, MO
Last spring frost
Apr 10
First fall frost
Oct 26
Growing season
199 days
Hardiness zone
6b
Explore more for O'Fallon, MO: full frost dates · planting calendar · Missouri frost dates
Climate data from the nearest NOAA station, Weldon Spring Nws, Mo (4.4 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.