Fontana Weather Forecast

    • 75
    • 103

    Hot

    • 74
    • 103

    Hot

    • 74
    • 98

    Hot

    • 73
    • 99

    Slight Chance Thunderstorms

    • 70
    • 96

    Slight Chance Thunderstorms

    • 66
    • 92

    Mostly Sunny

Today 21 Aug San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy this morning. Becoming mostly sunny. Highs 100 to 107. Light Winds becoming west 10 to 15 Mph this afternoon.

Tonight 21 Aug San Bernardino and Riverside County Valleys-The Inland Empire

Mostly clear. Lows 69 to 75. Areas of Winds west to 10 Mph in the evening becoming light.

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Fontana Temperature Statistics

August Temperature

Ontario International Airport (8.1 miles)

  • Lowest 1 August, 2025

    61.6 °F

  • Average August

    79.2 °F

  • Highest 7 August, 2025

    103.6 °F

Climate (2020–Present)

Ontario International Airport (8.1 miles)

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  • Average Low 2020–2025

    55.5 °F

  • Average 2020–2025

    66.7 °F

  • Average High 2020–2025

    79.1 °F
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