Cucamonga-Guasti Regional Park Weather Forecast

    • 62
    • 84

    Mostly Sunny

    • 65
    • 89

    Mostly Sunny

    • 68
    • 93

    Sunny

    • 68
    • 95

    Mostly Sunny

    • 69
    • 94

    Mostly Sunny

    • 69
    • 92

    Slight Chance Thunderstorms

    • 67
    • 90

    Slight Chance Thunderstorms

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

Partly cloudy with patchy fog this morning. Becoming sunny. Highs 82 to 88. Light Winds becoming west 10 to 15 Mph this afternoon.

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

Mostly clear. Lows 56 to 61. Areas of Winds west to 10 Mph this evening becoming light.

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Cucamonga-Guasti Regional Park Temperature Statistics

September Temperature

Ontario International Airport (1.2 miles)

  • Lowest 9 September, 2025

    63 °F

  • Average September

    78.8 °F

  • Highest 2 September, 2025

    102 °F

Climate (2020–Present)

Ontario International Airport (1.2 miles)

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  • Average Low 2020–2025

    55.5 °F

  • Average 2020–2025

    66.7 °F

  • Average High 2020–2025

    79.1 °F
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