Yes

you do need a jacket based on the weather in Dortmund, Germany 1 second ago

Why? Because it's quite chilly!
36°F2°C & Cloudy

Wind is 1 mph2 km/h from the Southeast, gusting to 3 mph5 km/h
December 26
11pm36°F2°C1 mph2 km/h SoutheastCloudy
December 27
12am35°F2°C2 mph2 km/h SoutheastCloudy
1am35°F2°C2 mph3 km/h SoutheastCloudy
2am35°F2°C2 mph3 km/h SoutheastCloudy
3am34°F1°C2 mph3 km/h SoutheastCloudy
4am35°F2°C2 mph3 km/h SoutheastCloudy
5am37°F3°C1 mph2 km/h SoutheastCloudy
6am38°F4°C1 mph2 km/h EastMostly Cloudy
7am40°F5°C1 mph2 km/h EastMostly Cloudy
8am43°F6°C1 mph2 km/h NortheastMostly Clear
9am42°F6°C2 mph3 km/h NorthMostly Clear
10am41°F5°C2 mph3 km/h NorthClear
DateLowHighWindDayNight
December 2633°F1°C43°F6°C2 mph3 km/h from EastPartly CloudyPartly Cloudy
December 2729°F-2°C38°F4°C2 mph3 km/h from WestMostly ClearPartly Cloudy
December 2829°F-1°C39°F4°C7 mph11 km/h from SouthwestMostly CloudyCloudy
December 2939°F4°C45°F7°C11 mph18 km/h from SouthwestCloudyMostly Cloudy
December 3037°F3°C45°F7°C13 mph21 km/h from SouthwestMostly CloudyWindy
December 3141°F5°C47°F8°C14 mph23 km/h from SouthwestDrizzleDrizzle
January 139°F4°C44°F7°C16 mph26 km/h from SouthwestWindyMostly Cloudy

Yes

Low of 29°F-2°C, High of 38°F4°C
Wind: 2 mph3 km/h
Precipitation: None

Support This Page