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Weather in Portsmouth for September 2025

Your guide to Portsmouth weather in September - trends and predictions

    Official Weather Alert ⚠️

  • Yellow Wind Warning - See hour by hour.

    • Temperatures

  • Until now, September 2025 in Portsmouth is slightly cooler than the historical average by -1.4 °C.

  • Expect cooler weather in the next days in Portsmouth with the forecast suggesting a temperature of 16.1 °C, lower than the historical average.

  • In general, the average temperature in Portsmouth at the beginning of September is 19.9 °C. As the month progressed, temperatures tended to significantly cool down, reaching an average of 15.1 °C by the end of September.

    • Rain 🌧️

  • Portsmouth experiences heavy rainfall in September, with over 20 rainy days and an average total precipitation 96 mm.

    • More

  • New! Chat with our AI weatherman - it’s amazing and free.

Average dry days
9
Dry days
Average rainy days
21
Rainy days
Average snowy days
0
Snow days
Average temperatures
18°/14°
Temperatures
Average wind speed
27 km/h
Avg max wind
Average humidity
76 %
Avg humidity

Portsmouth Weather September

Move between months or click on a day
August
October
Mon.Tue.Wed.Thu.Fri.Sat.Sun.
1
Light rain shower
19°
2
Light rain shower
19°
3
Light rain shower
20°
4
Light rain shower
20°
5
Sunny
19°
6
Sunny
21°
7
Sunny
21°
8
Patchy rain possible
20°
9
Partly cloudy
20°
10
Partly cloudy
21°
11
Partly cloudy
18°
12
Light rain shower
17°
13
Overcast
17°
14
Partly cloudy
18°
15
Weather Alert Patchy rain possible
17°
16
Patchy rain possible
17°
17
Patchy rain possible
18°
18
Patchy rain possible
19°
19
Cloudy
20°
20
Patchy rain possible
19°
21
Patchy rain possible
12°
22
Patchy rain possible
13°
23
Patchy rain possible
17°
24
Moderate rain
14°
25
Patchy rain possible
13°
26
Patchy rain possible
15°
27
Partly cloudy
16°
28
Sunny
15°
29
Overcast
16°
30
Partly cloudy
17°

Temperatures trend during September in Portsmouth

See the weather trend as well as the moving average line

September weather in Portsmouth day by day

Click on a date for more information
August October
Date Weather Temperatures Rain UV More
1 Sept. Light rain shower
Light rain shower
 19° /16° 6.9 mm 4
2 Sept. Light rain shower
Light rain shower
 19° /15° 3.1 mm 4
3 Sept. Light rain shower
Light rain shower
 20° /15° 2.6 mm 5
4 Sept. Light rain shower
Light rain shower
 20° /14° 2.9 mm 5
5 Sept. Sunny
Sunny
 19° /14° 5.2 mm 5
6 Sept. Sunny
Sunny
 21° /16° 6.2 mm 5
7 Sept. Sunny
Sunny
 21° /16° 1 mm 5
8 Sept. Patchy rain possible
Patchy rain possible
 20° /16° 2.1 mm 5
9 Sept. Partly cloudy
Partly cloudy
 20° /15° 0.3 mm 5
10 Sept. Partly cloudy
Partly cloudy
 21° /14° 2.4 mm 5
11 Sept. Partly cloudy
Partly cloudy
 18° /13° 2.1 mm 4
12 Sept. Light rain shower
Light rain shower
 17° /12° 2.6 mm 4
13 Sept. Overcast
Overcast
 17° /12° 3.3 mm 4
14 Sept. Partly cloudy
Partly cloudy
 18° /12° 1.3 mm 5
15 Sept. Patchy rain possible
Patchy rain possible
 17° /14° 0.9 mm 1
16 Sept. Patchy rain possible
Patchy rain possible
 17° /13° 0.4 mm 0.7
17 Sept. Patchy rain possible
Patchy rain possible
 18° /13° 2.9 mm 0.4
18 Sept. Patchy rain possible
Patchy rain possible
 19° /17° 0.3 mm 0.7
19 Sept. Cloudy
Cloudy
 20° /16° 0 mm 1
20 Sept. Patchy rain possible
Patchy rain possible
 19° /16° 1 mm 4
21 Sept. Patchy rain possible
Patchy rain possible
 12° /11° 0.3 mm 3
22 Sept. Patchy rain possible
Patchy rain possible
 13° /10° 0.3 mm 3
23 Sept. Patchy rain possible
Patchy rain possible
 17° /11° 1.4 mm 3
24 Sept. Moderate rain
Moderate rain
 14° /13° 11.9 mm 3
25 Sept. Patchy rain possible
Patchy rain possible
 13° /12° 0.9 mm 3
26 Sept. Patchy rain possible
Patchy rain possible
 15° /11° 0.5 mm 3
27 Sept. Partly cloudy
Partly cloudy
 16° /11° 0 mm 4
28 Sept. Sunny
Sunny
 15° /9° 0 mm 4
29 Sept. Overcast
Overcast
 16° /12° 2.7 mm 4
30 Sept. Partly cloudy
Partly cloudy
 17° /12° 6.6 mm 5
Next
Important Notice
Our weather forecast for Portsmouth in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the Portsmouth forecast closer to your planned date for the most up-to-date weather information.
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Portsmouth in September - FAQ

What are the expected maximum and minimum temperatures in Portsmouth during September?
Enjoy moderate daytime temperatures of up to 18° and cooler nights around 14°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Portsmouth during September?
Moderate rainfall is anticipated in Portsmouth during September, with a total of 96 mm spread over approximately 21 days. Considering plans for rainy days is advisable.
What are the typical wind conditions in Portsmouth during September?
The average wind speed in Portsmouth during September is 27 km/h, suggesting breezy to windy conditions, depending on your activities.

September rainfall patterns in Portsmouth

Explore the daily rainfall trends and prepare for Portsmouths September weather 💧

UV exposure in Portsmouth during September

Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️

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Get accurate weather forecasts for Portsmouth, located at latitude 50.799 and longitude -1.091. Stay updated with localized weather information tailored for Portsmouth.

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