Fontana Weather Forecast

    • 77
    • 105

    Hot

    • 74
    • 101

    Hot

    • 69
    • 95

    Mostly Sunny

    • 65
    • 89

    Sunny

    • 64
    • 85

    Sunny

    • 61
    • 84

    Sunny

    • 60
    • 81

    Sunny

Today 9 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Mostly sunny this Morning, then partly cloudy with a slight chance of Showers this afternoon. Hot. Highs 102 to 108. Areas of Winds north to 10 Mph becoming west this afternoon. Chance of measurable precipitation 20 percent.

Tonight 9 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Mostly clear this evening. Becoming partly cloudy. Lows 73 to 77. Areas of Winds west to 10 Mph this evening becoming light.

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Fontana Temperature Statistics

September Temperature

Ontario International Airport (8.1 miles)

  • Lowest 2 September, 2026

    63.6 °F

  • Average September

    76.6 °F

  • Highest 5 September, 2026

    95.6 °F

Climate (2021–2026)

Ontario International Airport (8.1 miles)

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  • Average Low 2021–2026

    55.8 °F

  • Average 2021–2026

    67.1 °F

  • Average High 2021–2026

    79.3 °F
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