Fullerton Weather Forecast

    • 55
    • 82

    Sunny

    • 53
    • 81

    Sunny

    • 53
    • 78

    Sunny

    • 53
    • 77

    Mostly Sunny

    • 53
    • 75

    Mostly Sunny

    • 51
    • 70

    Patchy Fog

Today 9 Dec Los Angeles County San Gabriel Valley

Sunny. Highs in the lower 80s.

Tonight 9 Dec Los Angeles County San Gabriel Valley

Clear. Lows in the mid 50s.

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Fullerton Temperature Statistics

December Temperature

Fullerton, Fullerton Municipal Airport (6.2 miles)

  • Lowest 5 December, 2025

    45 °F

  • Average December

    58.8 °F

  • Highest 1 December, 2025

    72 °F

Climate (2020–Present)

Fullerton, Fullerton Municipal Airport (6.2 miles)

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  • Average Low 2020–2025

    56.8 °F

  • Average 2020–2025

    66 °F

  • Average High 2020–2025

    76.4 °F
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