Rancho Fontana Weather Forecast

    • 60
    • 86

    Mostly Sunny

    • 59
    • 84

    Mostly Sunny

    • 57
    • 82

    Mostly Sunny

    • 57
    • 84

    Mostly Sunny

    • 57
    • 84

    Mostly Sunny

    • 55
    • 79

    Mostly Sunny

Today 20 May San Bernardino and Riverside County Valleys-The Inland Empire

Mostly sunny. Highs 85 to 91. Light Winds becoming west 10 to 15 Mph with Gusts to 25 Mph in the afternoon.

Tonight 20 May San Bernardino and Riverside County Valleys-The Inland Empire

Mostly clear in the evening. Becoming partly cloudy. Lows 52 to 55 in wind Sheltered Areas to 53 to 60 in warmer Locations. Areas of Winds west 10 to 15 Mph with Gusts to 25 Mph in the evening becoming light.

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Rancho Fontana Temperature Statistics

May Temperature

Ontario International Airport (7.5 miles)

  • Lowest 6 May, 2026

    49.6 °F

  • Average May

    67.9 °F

  • Highest 11 May, 2026

    96.7 °F

Climate (2021–Present)

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

    79.4 °F
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