St Helena Weather Forecast

    • 51
    • 81

    Becoming Sunny

    • 54
    • 84

    Mostly Sunny

    • 61
    • 93

    Mostly Sunny

    • 60
    • 98

    Mostly Sunny

    • 59
    • 97

    Mostly Sunny

    • 57
    • 94

    Mostly Sunny

Today 18 Aug North Bay Interior Valleys

Partly cloudy in the morning then becoming sunny. Patchy fog in the morning. Highs in the upper 60s to mid 80s. West Winds 5 to 10 Mph increasing to 10 to 20 Mph in the afternoon.

Tonight 18 Aug North Bay Interior Valleys

Mostly clear except patchy fog after midnight. Lows in the upper 40s to mid 50s. West Winds 5 to 15 Mph.

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St Helena Temperature Statistics

August Temperature

Petaluma Municipal Airport (18 miles)

  • Lowest 3 August, 2025

    46.4 °F

  • Average August

    62.7 °F

  • Highest 6 August, 2025

    87.8 °F

Climate (2020–Present)

Petaluma Municipal Airport (18 miles)

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  • Average Low 2020–2025

    44.5 °F

  • Average 2020–2025

    55.2 °F

  • Average High 2020–2025

    69.1 °F
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