O'Fallon, IL Weather & Growing Conditions
Today
60°F
Patchy Drizzle then Mostly Cloudy
Patchy drizzle before noon. Mostly cloudy, with a high near 60. West wind 8 to 13 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 60°F | Patchy Drizzle then Mostly Cloudy | 8 to 13 mph W | 12% |
| Tonight | 45°F | Partly Cloudy | 6 mph W | 0% |
| Thursday | 65°F | Sunny | 6 to 12 mph W | 0% |
| Thursday Night | 47°F | Partly Cloudy | 5 mph NW | 2% |
| Friday | 57°F | Partly Sunny | 6 to 13 mph N | 1% |
| Friday Night | 37°F | Partly Cloudy | 2 to 8 mph N | 0% |
| Saturday | 55°F | Mostly Sunny | 5 mph N | 0% |
| Saturday Night | 35°F | Partly Cloudy | 2 mph NW | 0% |
| Sunday | 59°F | Sunny | 2 to 7 mph NW | 1% |
| Sunday Night | 36°F | Clear | 2 mph W | 0% |
| Monday | 66°F | Sunny | 1 to 6 mph SW | 0% |
| Monday Night | 42°F | Clear | 2 mph SW | 0% |
| Tuesday | 69°F | Sunny | 5 mph W | 1% |
| Tuesday Night | 43°F | Mostly Clear | 1 mph N | 2% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for O'Fallon, IL
Last spring frost
Apr 12
First fall frost
Oct 20
Growing season
189 days
Hardiness zone
7a
Explore more for O'Fallon, IL: full frost dates · planting calendar · Illinois frost dates
Climate data from the nearest NOAA station, Belleville Siu Rsch, Il (6.7 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Nov 4, 2026.