No

Why? Because you should be inside at home! #StayHome

But if you absolutely had to go out to get groceries, medication or other essential travel, Yes, you do need a jacket.

Why? Because it's not very warm out.

Based on the weather in London, UK as of May 27, 2020 2:44am local time.

Now

Partly Cloudy
Temp: 58°F15°C
Wind: 4 MPH7 KPH
Precipitation: None

Today

Next 2 hours: Yes

Next 4 hours: Yes

Next 8 hours: Yes

Tomorrow

Yes

Partly cloudy throughout the day.
Low of 54°F12°C, High of 73°F23°C
Wind: 8 MPH13 KPH
Precipitation: 1% rain