Janesville Weather Forecast

    • 50
    • 77

    Decreasing Clouds

    • 49
    • 75

    Mostly Sunny

    • 53
    • 76

    Mostly Sunny

    • 63
    • 79

    Chance Rain Showers

    • 65
    • 78

    Chance Rain Showers

    • 62
    • 77

    Chance Rain Showers

Today 26 Sep Cumberland

Partly sunny. Near steady temperature in the mid 70s. East Winds around 5 Mph.

Tonight 26 Sep Cumberland

Partly cloudy. Lows around 50. East Winds around 5 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Janesville Temperature Statistics

September Temperature

Mattoon / Charleston, Coles County Memorial Airport (6.8 miles)

  • Lowest 14 September, 2026

    54.6 °F

  • Average September

    77.2 °F

  • Highest 2 September, 2026

    97.6 °F

Climate (2021–2026)

Mattoon / Charleston, Coles County Memorial Airport (6.8 miles)

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  • Average Low 2021–2026

    45.9 °F

  • Average 2021–2026

    55.5 °F

  • Average High 2021–2026

    65.1 °F
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