Petaluma River - Black John Slough Entrance Weather Forecast

    • 53
    • 83

    Increasing Clouds

    • 53
    • 75

    Mostly Cloudy

    • 53
    • 76

    Partly Sunny

    • 53
    • 78

    Mostly Sunny

    • 57
    • 86

    Mostly Sunny

    • 57
    • 88

    Mostly Sunny

    • 55
    • 82

    Partly Sunny

Today 19 Sep North Bay Interior Valleys

Sunny. Highs in the mid 70s to upper 80s. Southwest Winds 5 to 15 Mph.

Tonight 19 Sep North Bay Interior Valleys

Partly cloudy in the evening then becoming mostly cloudy. Patchy fog after midnight. Lows in the 50s to lower 60s. Southwest Winds 5 to 15 Mph.

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Petaluma River - Black John Slough Entrance Temperature Statistics

September Temperature

Novato / Gnoss Field (1.9 miles)

  • Lowest 6 September, 2026

    48.2 °F

  • Average September

    66.7 °F

  • Highest 9 September, 2026

    100.4 °F

Climate (2021–2026)

Novato / Gnoss Field (1.9 miles)

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  • Average Low 2021–2026

    47 °F

  • Average 2021–2026

    57.8 °F

  • Average High 2021–2026

    72.5 °F
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