Diamond Bar Weather Forecast

    • 70
    • 89

    Chance Rain

    • 71
    • 98

    Hot

    • 71
    • 101

    Hot

    • 68
    • 93

    Mostly Sunny

    • 65
    • 88

    Mostly Sunny

    • 63
    • 85

    Mostly Sunny

    • 63
    • 85

    Mostly Sunny

Today 7 Sep Los Angeles County San Gabriel Valley

Mostly cloudy in the Morning, becoming partly cloudy with a slight chance of Thunderstorms in the afternoon. Highs around 90. Chance of precipitation 20 percent.

Tonight 7 Sep Los Angeles County San Gabriel Valley

Partly cloudy. Lows around 70.

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  • Temperature Real-Time

Diamond Bar Temperature Statistics

September Temperature

Brackett Field Airport (4.3 miles)

  • Lowest 2 September, 2026

    60.8 °F

  • Average September

    76.7 °F

  • Highest 5 September, 2026

    89.6 °F

Climate (2021–2026)

Brackett Field Airport (4.3 miles)

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  • Average Low 2021–2026

    56 °F

  • Average 2021–2026

    68.1 °F

  • Average High 2021–2026

    76 °F
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