Fountain Valley Weather Forecast

    • 69
    • 82

    Rain Showers Likely

    • 67
    • 79

    Slight Chance Thunderstorms

    • 66
    • 80

    Partly Sunny

    • 67
    • 82

    Partly Sunny

    • 69
    • 84

    Partly Sunny

    • 67
    • 82

    Mostly Sunny

Today 18 Sep Orange County Inland

Mostly cloudy in the morning. Becoming partly cloudy. Showers likely and a slight chance of Thunderstorms. Highs 83 to 86. Areas of Winds south to 10 Mph. Chance of measurable precipitation 70 percent.

Tonight 18 Sep Orange County Inland

Partly cloudy with a slight chance of Thunderstorms. A chance of Showers. Lows 64 to 69. Areas of Winds south 10 Mph in the evening becoming light. Chance of measurable precipitation 40 percent.

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  • Temperature Forecast NOAA

  • Temperature Real-Time

Fountain Valley Temperature Statistics

September Temperature

John Wayne-Orange County Airport (5 miles)

  • Lowest 12 September, 2025

    64.9 °F

  • Average September

    72.6 °F

  • Highest 3 September, 2025

    86 °F

Climate (2020–Present)

John Wayne-Orange County Airport (5 miles)

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  • Average Low 2020–2025

    58.7 °F

  • Average 2020–2025

    65.7 °F

  • Average High 2020–2025

    73.6 °F
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