Yes

you do need a jacket based on the weather in Southampton SO16, UK 1 second ago

Why? Because it's cool. Pleasantly cool, but cool.
53°F11°C & Rain

Wind is 12 mph20 km/h from the SW, gusting to 24 mph38 km/h
April 25
12pm52°F11°C12 mph19 km/h SWCloudy
1pm51°F11°C11 mph17 km/h SWCloudy
2pm50°F10°C9 mph14 km/h SWCloudy
3pm49°F10°C6 mph10 km/h WCloudy
4pm48°F9°C5 mph8 km/h WMostly Cloudy
5pm47°F8°C4 mph7 km/h WMostly Cloudy
6pm46°F8°C4 mph6 km/h NWCloudy
7pm45°F7°C4 mph6 km/h NCloudy
8pm44°F7°C4 mph7 km/h NCloudy
9pm43°F6°C5 mph8 km/h NCloudy
10pm42°F6°C5 mph8 km/h NECloudy
11pm42°F5°C5 mph8 km/h NECloudy
DateLowHighWindDayNight
April 2437°F3°C55°F13°C8 mph13 km/h from WDrizzleCloudy
April 2541°F5°C54°F12°C8 mph12 km/h from EDrizzleDrizzle
April 2642°F5°C57°F14°C9 mph15 km/h from NEDrizzleRain
April 2742°F5°C55°F13°C11 mph18 km/h from WDrizzleMostly Clear
April 2839°F4°C59°F15°C10 mph16 km/h from SPartly CloudyPartly Cloudy
April 2944°F7°C58°F14°C8 mph13 km/h from SERainRain
April 3049°F9°C66°F19°C5 mph8 km/h from NEMostly CloudyMostly Cloudy

Yes

Low of 41°F5°C, High of 55°F13°C
Wind: 8 mph12 km/h
Precipitation: 54% rain

Support This Page