The climate of Southampton is oceanic, with quite cold, rainy winters and mild, relatively rainy summers.
The city is located in the south of England, near the coast of Hampshire. To the west of the city, we find the New Forest National Park, while to the south, beyond the stretch of sea called The Solent, we find the Isle of Wight.
The average temperature of the coldest month (February) is of 5.6 °C (42 °F), that of the warmest month (July) is of 18.1 °C (64 °F). The lowest record is -10 °C (14 °F), the highest is 35 °C (95 °F). Here are the average temperatures.
Southampton - Average temperatures
Min (°C)3346912141411953
Max (°C)891114182022222016129
Min (°F)373739434854575752484137
Max (°F)464852576468727268615448

Precipitation amounts to 780 millimeters (30.7 inches) per year: so, it is at an intermediate level. It ranges from 40 mm (1.6 in) in the driest month (July) to 95 mm (3.7 in) in the wettest ones (October, November). Here is the average precipitation.
Southampton - Average precipitation

On average, there are around 1,690 sunshine hours per year. Here are the average sunshine hours per day.
Southampton - Sunshine

The sea temperature ranges between 9 °C (48 °F) and 17 °C (63 °F). So, it never becomes warm for swimming. Here are the average sea temperatures.
Southampton - Sea temperature
Temp (°C)1098101114161717161411
Temp (°F)504846505257616363615752


Best Time

The best time to visit Southampton is the summer, from June to August, since it is the warmest of the year, although even in this season, it's better to bring a sweatshirt, a light jacket and an umbrella. The month of June is a bit cooler, so you may prefer July and August. September is a good month as well: it's a bit rainier than the summer months, but the temperatures are still pleasant, especially in the first part.
As previously mentioned, the sea is very cool even in summer, however, on sunny days, when the breeze is not too cool, you can sunbathe.