Yes

you do need a jacket based on the weather in Seattle, WA 98199, USA 1 second ago

Why? Because just cool enough for a jacket, but not warm enough to ditch it!
55°F13°C & Clear

Wind is 2 mph3 km/h from the Southeast, gusting to 4 mph6 km/h
September 22
12pm55°F13°C2 mph4 km/h SoutheastClear
1pm58°F14°C2 mph3 km/h SouthClear
2pm59°F15°C2 mph3 km/h WestClear
3pm61°F16°C2 mph3 km/h NorthwestClear
4pm63°F17°C3 mph4 km/h NorthwestClear
5pm64°F18°C5 mph7 km/h NorthMostly Clear
6pm65°F18°C6 mph9 km/h NorthMostly Cloudy
7pm67°F20°C6 mph9 km/h NorthPartly Cloudy
8pm67°F20°C6 mph10 km/h NorthMostly Clear
9pm66°F19°C6 mph9 km/h NorthMostly Clear
10pm63°F17°C6 mph9 km/h NorthMostly Clear
11pm60°F16°C6 mph9 km/h NorthMostly Clear
DateLowHighWindDayNight
September 2252°F11°C68°F20°C4 mph6 km/h from NorthMostly ClearClear
September 2353°F12°C71°F21°C7 mph11 km/h from NorthClearClear
September 2455°F13°C71°F22°C6 mph10 km/h from NorthClearClear
September 2553°F11°C66°F19°C4 mph6 km/h from NorthPartly CloudyMostly Cloudy
September 2652°F11°C65°F18°C4 mph6 km/h from NortheastPartly CloudyMostly Clear
September 2752°F11°C68°F20°C4 mph6 km/h from NorthMostly ClearPartly Cloudy
September 2855°F13°C68°F20°C5 mph8 km/h from SouthwestMostly CloudyCloudy

Yes

Low of 54°F12°C, High of 71°F22°C
Wind: 7 mph11 km/h
Precipitation: None

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