Alton Weather Forecast

    • 52
    • 68

    Mostly Cloudy

    • 51
    • 66

    Mostly Cloudy

    • 52
    • 66

    Mostly Cloudy

    • 52
    • 68

    Mostly Cloudy

    • 50
    • 67

    Mostly Cloudy

    • 51
    • 70

    Partly Sunny

    • 51
    • 71

    Mostly Cloudy

Today 18 Sep Northern Coastal Humboldt

Mostly cloudy. Lows 48 to 58. Highs 64 to 79.

Tonight 18 Sep Northern Coastal Humboldt

Partly cloudy early in the evening then becoming mostly cloudy. Patchy fog overnight. Lows 46 to 56. North wind around 10 Mph.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Alton Temperature Statistics

September Temperature

Fortuna Rohnerville Airport (0.6 miles)

  • Lowest 4 September, 2026

    46.4 °F

  • Average September

    58.1 °F

  • Highest 9 September, 2026

    82.4 °F

Climate (2021–2026)

Fortuna Rohnerville Airport (0.6 miles)

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  • Average Low 2021–2026

    45.4 °F

  • Average 2021–2026

    51.5 °F

  • Average High 2021–2026

    59.8 °F
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