Weather forecast for: O'Fallon IL
Last Update: 2:51 pm CDT Sep 4, 2026
Tonight: Mostly clear, with a low around 77. South wind around 5 mph becoming calm in the evening.
Saturday: Sunny and hot, with a high near 101. Heat index values as high as 109. Calm wind becoming northwest around 6 mph in the morning.
Saturday Night: Mostly clear, with a low around 74. North wind around 5 mph becoming calm.
Sunday: Mostly sunny, with a high near 94. Northeast wind 6 to 9 mph.
Sunday Night: Mostly clear, with a low around 67. East wind 5 to 9 mph.
Labor Day: Sunny, with a high near 91.
Monday Night: Mostly clear, with a low around 67.
Tuesday: Sunny and hot, with a high near 97.
Tuesday Night: Mostly clear, with a low around 75.
Wednesday: Sunny and hot, with a high near 100.
Wednesday Night: A 20 percent chance of showers and thunderstorms. Mostly clear, with a low around 75.
Thursday: A 20 percent chance of showers and thunderstorms. Mostly sunny, with a high near 93.
Thursday Night: A 20 percent chance of showers and thunderstorms. Partly cloudy, with a low around 68.
Friday: A 20 percent chance of showers and thunderstorms. Mostly sunny, with a high near 91.
WeatherWorld.com
