Fontana Weather Forecast

    • 59
    • 85

    Mostly Sunny

    • 61
    • 86

    Mostly Sunny

    • 67
    • 89

    Chance Rain Showers

    • 65
    • 87

    Chance Rain Showers

    • 66
    • 91

    Slight Chance Rain Showers

    • 69
    • 93

    Partly Sunny

    • 70
    • 94

    Mostly Sunny

Today 3 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Sunny. Highs 83 to 88. Areas of Winds south to 10 Mph becoming southwest with Gusts to 25 Mph this afternoon.

Tonight 3 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Mostly clear this evening. Becoming partly cloudy. Lows 52 to 59. Areas of Winds southwest 10 to 15 Mph with Gusts to 25 Mph this evening becoming light.

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Fontana Temperature Statistics

September Temperature

Ontario International Airport (8.1 miles)

  • Lowest 1 September, 2026

    64.9 °F

  • Average September

    74.7 °F

  • Highest 1 September, 2026

    89.1 °F

Climate (2021–2026)

Ontario International Airport (8.1 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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