Rancho Cucamonga Weather Forecast

    • 65
    • 90

    Mostly Sunny

    • 63
    • 89

    Mostly Sunny

    • 61
    • 85

    Mostly Sunny

    • 60
    • 84

    Mostly Sunny

    • 61
    • 86

    Sunny

    • 63
    • 89

    Sunny

    • 64
    • 90

    Mostly Sunny

Today 13 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy with patchy fog this morning. Becoming sunny. Highs 88 to 93. Light Winds becoming southwest 10 to 15 Mph this afternoon.

Tonight 13 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Mostly clear. Lows 58 to 65. Areas of Winds west 10 to 15 Mph this evening becoming light.

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Rancho Cucamonga Temperature Statistics

September Temperature

Ontario International Airport (3.7 miles)

  • Lowest 2 September, 2026

    63.6 °F

  • Average September

    81.5 °F

  • Highest 9 September, 2026

    109.7 °F

Climate (2021–2026)

Ontario International Airport (3.7 miles)

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  • Average Low 2021–2026

    55.8 °F

  • Average 2021–2026

    67.2 °F

  • Average High 2021–2026

    79.3 °F
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