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City of O'Fallon, MOO'Fallon, MO 7-Day Weather Forecast
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O'Fallon Weather Forecast
O'Fallon, MO Weather Forecast Date: 603 PM CDT Sun Sep 06 2026
Weather forecast for O'Fallon, MO
Tonight Lo: 65°F Lo: 18°C |
Tonight... Partly cloudy this evening, then becoming mostly cloudy. Lows in the mid 60s. Northeast winds 5 to 10 mph with gusts up to 20 mph. |
Labor Day Hi: 90°FHi: 32°C Lo: 65°F Lo: 18°C |
Labor Day... Sunny. Highs around 90. East winds 5 to 10 mph. |
| Tue Hi: 95°FHi: 35°C Lo: 71°F Lo: 22°C |
Tuesday... Mostly sunny. Hot with highs in the mid 90s. South winds around 5 mph. |
Wed Hi: 99°FHi: 37°C Lo: 69°F Lo: 21°C |
Wednesday... Mostly sunny. A slight chance of showers and thunderstorms in the afternoon. Hot with highs in the upper 90s. Chance of rain 20%. Heat index values up to 105 in the afternoon. |
| Thu Hi: 85°FHi: 29°C Lo: 61°F Lo: 16°C |
Thursday... Mostly cloudy in the morning, then becoming partly sunny. A slight chance of thunderstorms. A chance of showers, mainly in the morning. Not as warm with highs in the mid 80s. Chance of rain 50%. |
| Fri Hi: 85°FHi: 29°C Lo: 65°F Lo: 18°C |
Friday... Sunny. Highs in the mid 80s. |
| Sat Hi: 90°FHi: 32°C Lo: 69°F Lo: 21°C |
Saturday... Mostly sunny. A chance of showers with a slight chance of thunderstorms in the morning. Highs around 90. Chance of rain 30%. |
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