Cosmopolis Weather Forecast

    • 56
    • 69

    Rain Showers Likely

    • 47
    • 64

    Rain Showers Likely

    • 53
    • 69

    Mostly Sunny

    • 54
    • 79

    Partly Sunny

    • 49
    • 66

    Chance Rain Showers

    • 49
    • 66

    Partly Sunny

    • 51
    • 69

    Partly Sunny

Today 13 Sep Lower Chehalis River Valley

Mostly cloudy until late afternoon then becoming mostly sunny. Areas of fog in the Morning, then patchy fog late in the morning. Highs in the upper 60s to mid 70s. Light wind becoming southwest to 10 Mph in the afternoon.

Tonight 13 Sep Lower Chehalis River Valley

Patchy fog after midnight. A chance of rain late in the evening. Showers and a slight chance of Thunderstorms after Midnight, then rain likely late in the night. Rainfall Amounts a quarter to a half inch Possible, except higher Amounts possible in Thunderstorms. Lows in the mid to upper 50s. Southwest wind to 10 Mph becoming south after midnight.

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Cosmopolis Temperature Statistics

September Temperature

Hoquiam, Bowerman Airport (6.8 miles)

  • Lowest 2 September, 2025

    53.1 °F

  • Average September

    59.9 °F

  • Highest 2 September, 2025

    73 °F

Climate (2020–Present)

Hoquiam, Bowerman Airport (6.8 miles)

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  • Average Low 2020–2025

    46.2 °F

  • Average 2020–2025

    52.1 °F

  • Average High 2020–2025

    58.3 °F
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