Diamond Bar Weather Forecast

    • 44
    • 71

    Sunny

    • 46
    • 70

    Sunny

    • 48
    • 69

    Sunny

    • 51
    • 73

    Sunny

    • 52
    • 76

    Sunny

    • 54
    • 80

    Mostly Sunny

Today 4 Dec Los Angeles County San Gabriel Valley

Sunny. Highs in the upper 60s to mid 70s.

Tonight 4 Dec Los Angeles County San Gabriel Valley

Clear. Lows in the 40s to around 50.

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Diamond Bar Temperature Statistics

December Temperature

Brackett Field Airport (4.3 miles)

  • Lowest 2 December, 2025

    44.6 °F

  • Average December

    59.9 °F

  • Highest 1 December, 2025

    69.8 °F

Climate (2020–Present)

Brackett Field Airport (4.3 miles)

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  • Average Low 2020–2025

    55.5 °F

  • Average 2020–2025

    67.6 °F

  • Average High 2020–2025

    75.5 °F
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