Sonoma Mountain Weather Forecast

    • 59
    • 76

    Chance Rain Showers

    • 60
    • 72

    Partly Sunny

    • 60
    • 74

    Mostly Sunny

    • 62
    • 78

    Sunny

    • 63
    • 82

    Mostly Sunny

    • 62
    • 73

    Slight Chance Rain Showers

Today 18 Sep North Bay Interior Valleys

Mostly cloudy. A slight chance of Showers. Isolated Thunderstorms in the afternoon. Highs in the upper 60s to mid 80s. South Winds 10 to 15 Mph.

Tonight 18 Sep North Bay Interior Valleys

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

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Sonoma Mountain Temperature Statistics

September Temperature

Petaluma Municipal Airport (4.3 miles)

  • Lowest 14 September, 2025

    48.2 °F

  • Average September

    63.2 °F

  • Highest 1 September, 2025

    93.2 °F

Climate (2020–Present)

Petaluma Municipal Airport (4.3 miles)

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  • Average Low 2020–2025

    44.4 °F

  • Average 2020–2025

    55.2 °F

  • Average High 2020–2025

    69.1 °F
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