Fullerton Weather Forecast

    • 68
    • 84

    Rain Showers Likely

    • 65
    • 82

    Chance Rain Showers

    • 64
    • 84

    Mostly Sunny

    • 66
    • 86

    Mostly Sunny

    • 68
    • 89

    Mostly Sunny

    • 65
    • 87

    Mostly Sunny

Today 18 Sep Los Angeles County San Gabriel Valley

Showers likely. Slight a chance of Thunderstorms. Highs in the lower to mid 80s. Chance of precipitation 70 percent.

Tonight 18 Sep Los Angeles County San Gabriel Valley

Mostly cloudy with a chance of Showers and a slight chance of Thunderstorms. Lows in the mid 60s to around 70. Chance of precipitation 50 percent.

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Fullerton Temperature Statistics

September Temperature

Fullerton, Fullerton Municipal Airport (6.2 miles)

  • Lowest 11 September, 2025

    64.9 °F

  • Average September

    74.4 °F

  • Highest 2 September, 2025

    97 °F

Climate (2020–Present)

Fullerton, Fullerton Municipal Airport (6.2 miles)

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  • Average Low 2020–2025

    56.7 °F

  • Average 2020–2025

    66.1 °F

  • Average High 2020–2025

    76.7 °F
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