Cucamonga-Guasti Regional Park Weather Forecast

    • 69
    • 90

    Rain Showers Likely

    • 69
    • 82

    Rain Showers Likely

    • 71
    • 91

    Mostly Sunny

    • 73
    • 93

    Partly Sunny

    • 73
    • 97

    Hot

    • 71
    • 96

    Mostly Sunny

    • 67
    • 93

    Mostly Sunny

Today 5 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Mostly sunny. Highs 88 to 93. Areas of Winds south to 10 Mph becoming southwest with Gusts to 25 Mph this afternoon.

Tonight 5 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Mostly clear this Evening, then mostly cloudy with a slight chance of Showers overnight. Lows 63 to 69. Areas of Winds southwest to 10 Mph this evening becoming light. Chance of measurable precipitation 20 percent.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Cucamonga-Guasti Regional Park Temperature Statistics

September Temperature

Ontario International Airport (1.2 miles)

  • Lowest 3 September, 2026

    63 °F

  • Average September

    75.2 °F

  • Highest 1 September, 2026

    90.6 °F

Climate (2021–2026)

Ontario International Airport (1.2 miles)

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  • Average Low 2021–2026

    55.8 °F

  • Average 2021–2026

    67.2 °F

  • Average High 2021–2026

    79.4 °F
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