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Big Flat Lake, IL Weather Forecast
Big Flat Lake, IL Weather Forecast Date: 553 AM CDT Thu Sep 10 2026
The area/counties/county of: Clinton County Il, including the cities of: Centralia and Salem.or toggle through each period.
Today... A chance of thunderstorms. Showers. Much cooler with highs in the lower 80s. Southeast winds around 5 mph, becoming northwest around 5 mph this afternoon. Chance of rain 90%.
Tonight... Mostly cloudy. A slight chance of showers and thunderstorms in the evening. Patchy fog after midnight. Lows in the mid 60s. North winds around 5 mph in the evening, becoming light and variable. Chance of rain 20%.
Friday... Mostly cloudy. A slight chance of showers in the morning, then a chance of showers in the afternoon. Highs in the lower 80s. East winds around 5 mph. Chance of rain 30%.
Friday Night... Partly cloudy. A chance of showers in the evening. Lows in the upper 60s. Light and variable winds. Chance of rain 30%.
Saturday... Mostly sunny. A slight chance of showers and thunderstorms in the afternoon. Highs in the upper 80s. Southwest winds around 5 mph. Chance of rain 20%.
Saturday Night... Partly cloudy. A slight chance of showers in the evening. Lows in the upper 60s. Chance of rain 20%.
Sunday... Mostly sunny. Highs in the upper 80s.
Sunday Night... Mostly clear. Lows in the upper 60s. Highs in the lower 90s. Heat index values up to 100.
Monday... Mostly clear. Lows in the upper 60s. Highs in the lower 90s. Heat index values up to 100.
Tuesday... Sunny. A chance of showers with a slight chance of thunderstorms in the afternoon. Highs in the upper 80s. Chance of rain 40%.
Tuesday Night... A slight chance of thunderstorms in the evening. Partly cloudy with a chance of showers. Lows in the mid 60s. Chance of rain 40%.
POP = Probability of Precipitation
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