Yes

you do need a jacket based on the weather in Leiden, Netherlands 1 second ago

Why? Because it's pretty chilly!
50°F10°C & Mostly Cloudy

Wind is 7 mph12 km/h from the South, gusting to 15 mph24 km/h
October 30
9pm50°F10°C8 mph12 km/h SouthMostly Cloudy
10pm49°F10°C8 mph13 km/h SouthMostly Cloudy
11pm49°F9°C10 mph15 km/h SouthCloudy
October 31
12am48°F9°C10 mph16 km/h SouthCloudy
1am48°F9°C10 mph16 km/h SouthMostly Cloudy
2am48°F9°C10 mph16 km/h SouthCloudy
3am48°F9°C10 mph17 km/h SouthCloudy
4am48°F9°C11 mph17 km/h SouthCloudy
5am48°F9°C11 mph17 km/h SouthCloudy
6am48°F9°C11 mph18 km/h SouthCloudy
7am49°F9°C11 mph17 km/h SouthCloudy
8am50°F10°C10 mph17 km/h SouthCloudy
DateLowHighWindDayNight
October 2949°F9°C55°F13°C6 mph10 km/h from WestMostly CloudyCloudy
October 3048°F9°C57°F14°C10 mph17 km/h from SouthDrizzleMostly Clear
October 3150°F10°C58°F14°C14 mph22 km/h from SouthwestRainMostly Cloudy
November 148°F9°C54°F12°C11 mph18 km/h from SouthwestDrizzlePartly Cloudy
November 246°F8°C55°F13°C17 mph27 km/h from SouthwestDrizzleWindy
November 351°F10°C57°F14°C14 mph22 km/h from SouthMostly CloudyCloudy
November 450°F10°C57°F14°C11 mph18 km/h from SouthMostly CloudyCloudy

Yes

Low of 47°F9°C, High of 57°F14°C
Wind: 10 mph17 km/h
Precipitation: 31% rain

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