Click on a day for an hourly weather forecast
The weather in Portsmouth in September is hot. The average temperatures are between 21°C and 27°C.
You can expect about 3 to 8 days of rain in Portsmouth during the month of September. It’s a good idea to bring along your umbrella so that you don’t get caught in poor weather.
Our weather forecast can give you a great sense of what weather to expect in Portsmouth in September 2025.
If you’re planning to visit Portsmouth in the near future, we highly recommend that you review the 14 day weather forecast for Portsmouth before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | 8° / 2° | 5 | 23 | 3 | 73 mm | Bad | Portsmouth in January |
| February | 9° / 3° | 6 | 20 | 3 | 77 mm | Bad | Portsmouth in February |
| March | 13° / 6° | 7 | 23 | 1 | 87 mm | Bad | Portsmouth in March |
| April | 18° / 11° | 5 | 25 | 0 | 90 mm | Good | Portsmouth in April |
| May | 23° / 16° | 7 | 24 | 0 | 127 mm | Good | Portsmouth in May |
| June | 28° / 21° | 7 | 24 | 0 | 120 mm | Good | Portsmouth in June |
| July | 31° / 23° | 7 | 24 | 0 | 142 mm | Ok | Portsmouth in July |
| August | 30° / 23° | 7 | 24 | 0 | 158 mm | Ok | Portsmouth in August |
| September | 27° / 21° | 5 | 25 | 0 | 155 mm | Perfect | Portsmouth in September |
| October | 22° / 15° | 3 | 28 | 0 | 93 mm | Good | Portsmouth in October |
| November | 15° / 9° | 5 | 25 | 0 | 70 mm | Good | Portsmouth in November |
| December | 11° / 5° | 6 | 23 | 1 | 80 mm | Ok | Portsmouth in December |