Rancho Fontana Weather Forecast

    • 64
    • 89

    Mostly Cloudy

    • 62
    • 85

    Mostly Cloudy

    • 60
    • 86

    Mostly Sunny

    • 63
    • 88

    Mostly Sunny

    • 64
    • 91

    Mostly Sunny

    • 64
    • 91

    Mostly Sunny

Today 12 Aug San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy. Highs 87 to 93. Areas of Winds southwest to 10 Mph becoming west with Gusts to 30 Mph this afternoon.

Tonight 12 Aug San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy in the evening. Becoming mostly cloudy. Lows 59 to 64. Areas of Winds west 10 to 15 Mph with Gusts to 25 Mph becoming southwest overnight.

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Rancho Fontana Temperature Statistics

August Temperature

Ontario International Airport (7.5 miles)

  • Lowest 5 August, 2026

    66.7 °F

  • Average August

    84 °F

  • Highest 1 August, 2026

    102.7 °F

Climate (2021–2026)

Ontario International Airport (7.5 miles)

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  • Average Low 2021–2026

    55.8 °F

  • Average 2021–2026

    67.1 °F

  • Average High 2021–2026

    79.3 °F
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