Diamond Bar Weather Forecast

    • 56
    • 79

    Becoming Sunny

    • 58
    • 84

    Sunny

    • 57
    • 84

    Mostly Sunny

    • 56
    • 82

    Mostly Sunny

    • 55
    • 79

    Mostly Sunny

    • 55
    • 79

    Mostly Sunny

Today 18 May Los Angeles County San Gabriel Valley

Mostly cloudy this Morning, then sunny. Highs around 80.

Tonight 18 May Los Angeles County San Gabriel Valley

Mostly clear. Lows in the upper 50s.

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Diamond Bar Temperature Statistics

May Temperature

Brackett Field Airport (4.3 miles)

  • Lowest 6 May, 2026

    51.8 °F

  • Average May

    67.7 °F

  • Highest 11 May, 2026

    89.6 °F

Climate (2021–Present)

Brackett Field Airport (4.3 miles)

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  • Average Low 2021–2026

    56 °F

  • Average 2021–2026

    68 °F

  • Average High 2021–2026

    76 °F
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