Grass Valley Reservoir Weather Forecast

    • 57
    • 77

    Rain Showers

    • 55
    • 77

    Mostly Sunny

    • 56
    • 76

    Mostly Sunny

    • 54
    • 76

    Sunny

    • 53
    • 77

    Sunny

    • 54
    • 79

    Mostly Sunny

Today 13 Sep Southern Mountains

Partly cloudy with scattered rain Showers and isolated Thunderstorms in the Morning, then partly sunny with scattered Showers and Thunderstorms in the afternoon. Highs in the lower 60s. Chance of precipitation 50 percent.

Tonight 13 Sep Southern Mountains

Isolated Showers and Thunderstorms in the Evening, then isolated rain Showers after midnight. Partly cloudy. Lows around 50. Chance of precipitation 20 percent.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Grass Valley Reservoir Temperature Statistics

September Temperature

St George Municipal Airport (25.5 miles)

  • Lowest 7 September, 2026

    62.1 °F

  • Average September

    82.1 °F

  • Highest 10 September, 2026

    102.9 °F

Climate (2021–2026)

St George Municipal Airport (25.5 miles)

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  • Average Low 2021–2026

    53 °F

  • Average 2021–2026

    64.8 °F

  • Average High 2021–2026

    76.8 °F
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