Ontario Weather Forecast

    • 68
    • 93

    Sunny

    • 68
    • 93

    Sunny

    • 69
    • 93

    Mostly Sunny

    • 67
    • 92

    Partly Sunny

    • 62
    • 85

    Partly Sunny

    • 62
    • 83

    Mostly Sunny

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

Mostly sunny. Highs 88 to 93.

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 this evening becoming light.

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Ontario Temperature Statistics

September Temperature

Ontario International Airport (3.7 miles)

  • Lowest 19 September, 2026

    61.6 °F

  • Average September

    78.9 °F

  • Highest 9 September, 2026

    109.7 °F

Climate (2021–2026)

Ontario International Airport (3.7 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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