Diamond Bar Weather Forecast

    • 67
    • 95

    Becoming Sunny

    • 66
    • 92

    Mostly Cloudy

    • 64
    • 85

    Rain Showers Likely

    • 65
    • 81

    Slight Chance Thunderstorms

    • 64
    • 85

    Mostly Sunny

    • 67
    • 86

    Mostly Sunny

Today 16 Sep Los Angeles County San Gabriel Valley

Sunny after morning low Clouds and fog. Highs in the lower to mid 90s.

Tonight 16 Sep Los Angeles County San Gabriel Valley

Mostly clear in the evening then partly cloudy. Lows in the mid 60s to around 70.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Diamond Bar Temperature Statistics

September Temperature

Brackett Field Airport (4.3 miles)

  • Lowest 9 September, 2025

    59 °F

  • Average September

    80.9 °F

  • Highest 2 September, 2025

    102.2 °F

Climate (2020–Present)

Brackett Field Airport (4.3 miles)

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  • Average Low 2020–2025

    55.6 °F

  • Average 2020–2025

    67.8 °F

  • Average High 2020–2025

    75.7 °F
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