Guerneville Weather Forecast

    • 57
    • 81

    Chance Rain Showers

    • 56
    • 77

    Decreasing Clouds

    • 56
    • 78

    Mostly Sunny

    • 59
    • 84

    Sunny

    • 58
    • 87

    Mostly Sunny

    • 58
    • 81

    Slight Chance Rain Showers

    • 56
    • 76

    Partly Sunny

Today 18 Sep North Bay Interior Valleys

Mostly cloudy late in the morning then becoming partly cloudy. A slight chance of Showers. Isolated Thunderstorms in the afternoon. Highs in the lower 70s to mid 80s. South Winds 5 to 15 Mph.

Tonight 18 Sep North Bay Interior Valleys

Mostly cloudy. Isolated Thunderstorms in the evening. A chance of Showers. Patchy fog after midnight. Lows in the mid 50s to lower 60s. Southwest Winds 5 to 10 Mph.

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Guerneville Temperature Statistics

September Temperature

Santa Rosa, Santa Rosa Sonoma County Airport (9.3 miles)

  • Lowest 14 September, 2025

    48 °F

  • Average September

    65.9 °F

  • Highest 1 September, 2025

    99 °F

Climate (2020–Present)

Santa Rosa, Santa Rosa Sonoma County Airport (9.3 miles)

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  • Average Low 2020–2025

    45.3 °F

  • Average 2020–2025

    57.9 °F

  • Average High 2020–2025

    72.8 °F
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