Lostmans River - Onion Key Weather Forecast

    • 70
    • 89

    Becoming Sunny

    • 70
    • 88

    Partly Sunny

    • 72
    • 88

    Partly Sunny

    • 73
    • 87

    Thunderstorms

    • 73
    • 89

    Rain Showers

    • 75
    • 89

    Thunderstorms Likely

    • 75
    • 89

    Rain Showers Likely

Today 26 Sep Mainland Monroe

Mostly sunny with a chance of Thunderstorms. A chance of Showers in the Morning, then Showers likely in the afternoon. Highs in the upper 80s. Chance of rain 70 percent.

Tonight 26 Sep Mainland Monroe

Mostly clear. Lows around 70. Northwest Winds 5 to 10 Mph, becoming north after midnight.

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Lostmans River - Onion Key Temperature Statistics

September Temperature

Miami, Kendall-Tamiami Executive Airport (43.5 miles)

  • Lowest 17 September, 2026

    81.6 °F

  • Average September

    85.2 °F

  • Highest 13 September, 2026

    90 °F

Climate (2021–2026)

Miami, Kendall-Tamiami Executive Airport (43.5 miles)

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  • Average Low 2021–2026

    68.8 °F

  • Average 2021–2026

    77.1 °F

  • Average High 2021–2026

    85.7 °F
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