Yes

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

Why? Because the drizzle is not enough rain to call it "raining," but enough to make you a little soggy!
65°F18°C & Drizzle

Wind is 3 mph5 km/h from the North, gusting to 11 mph17 km/h
July 2
1am65°F18°C4 mph6 km/h NorthCloudy
2am65°F19°C6 mph9 km/h NorthCloudy
3am66°F19°C5 mph7 km/h NorthCloudy
4am68°F20°C5 mph7 km/h NorthCloudy
5am68°F20°C4 mph7 km/h NorthwestDrizzle
6am70°F21°C5 mph9 km/h WestDrizzle
7am69°F21°C6 mph10 km/h WestDrizzle
8am69°F21°C8 mph13 km/h NorthwestDrizzle
9am70°F21°C10 mph15 km/h NorthwestCloudy
10am70°F21°C11 mph18 km/h NorthwestMostly Cloudy
11am71°F22°C11 mph19 km/h NorthwestMostly Cloudy
12pm73°F23°C12 mph19 km/h NorthwestPartly Cloudy
DateLowHighWindDayNight
July 160°F15°C74°F23°C8 mph13 km/h from NorthwestDrizzleClear
July 253°F12°C75°F24°C5 mph9 km/h from NorthwestMostly ClearMostly Clear
July 356°F13°C77°F25°C7 mph11 km/h from WestMostly CloudyMostly Cloudy
July 459°F15°C73°F23°C12 mph20 km/h from SouthwestCloudyDrizzle
July 559°F15°C70°F21°C11 mph17 km/h from WestMostly CloudyMostly Cloudy
July 656°F13°C66°F19°C12 mph19 km/h from NorthwestMostly CloudyPartly Cloudy
July 755°F13°C67°F20°C8 mph12 km/h from WestRainMostly Clear

Yes

Low of 54°F12°C, High of 75°F24°C
Wind: 5 mph9 km/h
Precipitation: None

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