Fontana Weather Forecast

    • 61
    • 86

    Increasing Clouds

    • 61
    • 82

    Mostly Sunny

    • 61
    • 83

    Mostly Sunny

    • 63
    • 86

    Sunny

    • 64
    • 89

    Mostly Sunny

    • 62
    • 87

    Mostly Sunny

    • 62
    • 85

    Mostly Sunny

Today 15 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy with patchy fog this morning. Becoming sunny. Highs 83 to 88. Areas of Winds south to 10 Mph becoming southwest with Gusts to 25 Mph this afternoon.

Tonight 15 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy this evening. Becoming mostly cloudy. Lows 52 to 60. Areas of Winds southwest 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

    81.4 °F

  • Highest 9 September, 2026

    109.7 °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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