Yes

you do need a jacket based on the weather in Stockholm, Sweden 1 second ago

Why? Because it's not very warm out and it's on the windy side!
58°F14°C & Mostly Cloudy

Wind is 11 mph17 km/h from the Southwest, gusting to 24 mph39 km/h
September 18
5pm58°F14°C11 mph18 km/h WestMostly Cloudy
6pm57°F14°C11 mph18 km/h WestMostly Cloudy
7pm56°F14°C11 mph18 km/h WestPartly Cloudy
8pm56°F13°C11 mph18 km/h WestPartly Cloudy
9pm56°F13°C11 mph17 km/h WestPartly Cloudy
10pm55°F13°C10 mph16 km/h WestPartly Cloudy
11pm55°F13°C10 mph16 km/h WestPartly Cloudy
September 19
12am55°F13°C9 mph15 km/h WestPartly Cloudy
1am55°F13°C9 mph14 km/h WestMostly Clear
2am56°F13°C9 mph14 km/h WestMostly Clear
3am57°F14°C11 mph17 km/h WestPartly Cloudy
4am59°F15°C11 mph18 km/h WestPartly Cloudy
DateLowHighWindDayNight
September 1752°F11°C63°F17°C5 mph8 km/h from SouthwestPartly CloudyDrizzle
September 1855°F13°C66°F19°C9 mph15 km/h from WestPartly CloudyCloudy
September 1961°F16°C68°F20°C10 mph17 km/h from WestMostly CloudyDrizzle
September 2056°F13°C67°F20°C11 mph17 km/h from SouthwestDrizzleDrizzle
September 2148°F9°C57°F14°C10 mph16 km/h from WestMostly ClearPartly Cloudy
September 2245°F7°C55°F13°C6 mph10 km/h from NorthwestDrizzleMostly Clear
September 2342°F6°C55°F13°C7 mph12 km/h from NorthwestClearClear

Yes

Low of 55°F13°C, High of 66°F19°C
Wind: 9 mph15 km/h
Precipitation: None

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