Fontana Weather Forecast

    • 70
    • 81

    Rain Showers Likely

    • 72
    • 91

    Mostly Sunny

    • 74
    • 94

    Mostly Sunny

    • 75
    • 99

    Hot

    • 74
    • 98

    Hot

    • 68
    • 94

    Mostly Sunny

    • 65
    • 89

    Sunny

Today 6 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Cloudy with Showers likely this Morning, then mostly cloudy with a chance of Showers and a slight chance of Thunderstorms this afternoon. Highs 80 to 85. Areas of Winds north to 10 Mph this morning becoming light. Chance of measurable precipitation 70 percent.

Tonight 6 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy. Lows 66 to 70. Light Winds.

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Fontana Temperature Statistics

September Temperature

Ontario International Airport (8.1 miles)

  • Lowest 4 September, 2026

    63 °F

  • Average September

    75.4 °F

  • Highest 1 September, 2026

    90.6 °F

Climate (2021–2026)

Ontario International Airport (8.1 miles)

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  • Average Low 2021–2026

    55.8 °F

  • Average 2021–2026

    67.2 °F

  • Average High 2021–2026

    79.3 °F
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