Rancho Cucamonga Weather Forecast

    • 55
    • 80

    Becoming Sunny

    • 58
    • 86

    Mostly Sunny

    • 58
    • 85

    Mostly Sunny

    • 58
    • 86

    Mostly Sunny

    • 58
    • 84

    Mostly Sunny

    • 57
    • 83

    Mostly Sunny

Today 18 May San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy with patchy fog in the morning. Becoming mostly sunny. Highs 77 to 83. Areas of Winds north 10 to 20 Mph with Gusts to 35 Mph becoming west with Gusts to 30 Mph in the afternoon.

Tonight 18 May San Bernardino and Riverside County Valleys-The Inland Empire

Partly cloudy in the evening. Becoming mostly clear. Lows around 50 in wind Sheltered Areas to 49 to 55 in warmer Locations. Areas of Winds west 10 to 20 Mph with Gusts to 30 Mph in the evening becoming light.

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Rancho Cucamonga Temperature Statistics

May Temperature

Ontario International Airport (3.7 miles)

  • Lowest 6 May, 2026

    49.6 °F

  • Average May

    68.1 °F

  • Highest 11 May, 2026

    96.7 °F

Climate (2021–Present)

Ontario International Airport (3.7 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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