Portsmouth weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Good
Best time to visit: May – September
What is the weather like in Portsmouth in September?
In September, Portsmouth is mild: daytime highs average 19 °C, and nights cool down to about 12 °C. The sea averages 17.6 °C – bracing, so a wetsuit helps for longer swims. Expect around 6 hours of sunshine a day. Rain falls on about 9 days, adding up to 53 mm. All in all, September is a good month for a holiday in Portsmouth.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 80 | 78 | 49 |
| Day | 21° | 19° | 15° |
| Night | 14° | 12° | 10° |
| Sea | 18° | 18° | 16° |
| Sun | 7 h | 6 h | 4 h |
| Rain days | 10 | 9 | 13 |
More details for September
- Daylight
- 12 h 43 min06:38 – 19:21
- UV index
- 4 · moderateclear sky, noon (estimate)All months
- Muggy days
- 0 daysdew point 18 °C or moreAll months
- Wind
- 23 km/haverage daily peakAll months
- Cloud cover
- 63 %on averageAll months
- Hot days
- 0 days30 °C or more
- Time zone
- UTC+1Europe/London
How the score comes together
- Temperatureweight 50 %100 %
- Sunshineweight 20 %45 %
- Few rainy daysweight 30 %65 %
Each factor is rated from 0 to 100 % and weighted for the travel style “City break”.
What to pack in September
- Wetsuit for longer swims
- Sunscreen
- A jumper for the evenings
- Rain jacket or umbrella
Portsmouth in September: quick answers
Is Portsmouth hot in September?
No. In September, Portsmouth is mild: daytime highs average 19 °C and nights drop to about 12 °C.
Can you swim in Portsmouth in September?
Only if you don't mind cold water: in September the sea averages just 17.6 °C. Comfortable swimming temperatures are not reached at any time of year.
Does it rain much in Portsmouth in September?
Rain falls on about 9 days, adding up to 53 mm.
Portsmouth month by month
The whole year in PortsmouthAll destinations: United KingdomWhere to go in SeptemberSea temperature in September
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences