Fontana Weather Forecast

    • 64
    • 87

    Mostly Sunny

    • 64
    • 85

    Mostly Cloudy

    • 62
    • 80

    Mostly Sunny

    • 65
    • 85

    Sunny

    • 69
    • 93

    Mostly Sunny

    • 70
    • 94

    Mostly Sunny

Today 19 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy in the morning. Becoming sunny. Highs 85 to 90. Light Winds becoming west 10 to 15 Mph in the afternoon.

Tonight 19 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Mostly clear in the evening. Becoming partly cloudy. Lows 54 to 62. Areas of Winds west to 10 Mph in the 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

    80.2 °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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