Portsmouth Harbour - Portchester Lake Weather Forecast

    • 12
    • 24

    Partly cloudy

    • 14
    • 19

    Cloudy

    • 13
    • 20

    Cloudy

    • 16
    • 19

    Cloudy

    • 19
    • 22

    Cloudy

    • 16
    • 20

    Sunny day

    • 13
    • 19

    Light rain shower

Today 25 Sep London and South East England

A grey start in the west with low cloud, mist and fog but much clearer in the east. Widely fine with good sunny spells once the low cloud breaks. Cloud builds late in the afternoon. Very warm in the sun. Maximum temperature 27 °C.

Tonight 25 Sep London and South East England

Cloud continues to increase and rain develops through the evening. Rain clears overnight but cloud lingering for many into Saturday. A milder night for most, but cool where skies clear. Minimum temperature 6 °C.

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Portsmouth Harbour - Portchester Lake Temperature Statistics

September Temperature

Thorney Island (13km)

  • Lowest 21 September, 2026

    8.8 °C

  • Average September

    17.3 °C

  • Highest 3 September, 2026

    23.5 °C

Climate (2021–2026)

Thorney Island (13km)

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  • Average Low 2021–2026

    9 °C

  • Average 2021–2026

    12.4 °C

  • Average High 2021–2026

    15.6 °C
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