Rancho Fontana Weather Forecast

    • 69
    • 95

    Sunny

    • 69
    • 94

    Mostly Sunny

    • 69
    • 93

    Mostly Sunny

    • 67
    • 91

    Partly Sunny

    • 61
    • 84

    Partly Sunny

    • 61
    • 82

    Mostly Sunny

Today 23 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Sunny, warmer. Highs 93 to 98. Light Winds becoming west 10 to 15 Mph with Gusts to 25 Mph this afternoon.

Tonight 23 Sep San Bernardino and Riverside County Valleys-The Inland Empire

Clear. Lows 63 to 68. Areas of Winds west 10 to 15 Mph in the evening becoming light.

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Rancho Fontana Temperature Statistics

September Temperature

Ontario International Airport (7.5 miles)

  • Lowest 19 September, 2026

    61.6 °F

  • Average September

    79.1 °F

  • Highest 9 September, 2026

    109.7 °F

Climate (2021–2026)

Ontario International Airport (7.5 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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