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City of O'Fallon, MOO'Fallon, MO Weather Forecast
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O'Fallon Weather Forecast
| TODAY | TONIGHT | MONDAY | MONDAY NIGHT | TUESDAY | TUESDAY NIGHT | WEDNESDAY | WEDNESDAY NIGHT | THURSDAY | THURSDAY NIGHT | FRIDAY | FRIDAY NIGHT |
 |  |  | | | | |  | | |  |  |
| Sunny | Partly Cloudy | Mostly Cloudy | Partly Cloudy | Mostly Cloudy | Partly Cloudy | Sunny | Clear | Sunny | Partly Cloudy | Partly Cloudy | Mostly Cloudy |
| Hi: 79°FHi: 26°C | Lo: 51°FLo: 11°C | Hi: 79°FHi: 26°C | Lo: 51°FLo: 11°C | Hi: 75°FHi: 24°C | Lo: 51°FLo: 11°C | Hi: 80°FHi: 27°C | Lo: 55°FLo: 13°C | Hi: 81°FHi: 27°C | Hi: 80°FHi: 27°C Lo: 55°FLo: 13°C | Hi: 80°FHi: 27°C Lo: 55°FLo: 13°C | Lo: 59°FLo: 15°C |
POP = Probability of Precipitation.
Weather Outlook Updated: 624 AM CDT Sun Oct 25 2026 
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Issued: 600 AM CDT Sun Oct 25 2026
Key Messages
- Warm days and crisp fall nights continue through the end of the coming workweek.
- Rain chances return for Halloween weekend.
Aviation
/06Z TAFS THROUGH 12Z MONDAY/... Issued at 559 AM CDT Sun Oct 25 2026
Dry/VFR conditions with light and variable winds and scattered to broken high clouds are forecast through the period.
Watches / Warnings / Advisories
/WARNINGS/ADVISORIES... MO...None. IL...None.