Yes

you do need a jacket based on the weather in Lancing BN15, UK 1 second ago

Why? Because the wind is harsh and biting!
60°F15°C & Windy

Wind is 15 mph24 km/h from the West, gusting to 24 mph39 km/h
September 10
6pm60°F15°C15 mph25 km/h WestWindy
7pm58°F15°C15 mph24 km/h WestWindy
8pm57°F14°C15 mph24 km/h WestClear
9pm56°F14°C14 mph23 km/h WestClear
10pm56°F13°C12 mph20 km/h WestClear
11pm55°F13°C12 mph19 km/h WestClear
September 11
12am56°F13°C12 mph20 km/h WestMostly Clear
1am56°F14°C13 mph21 km/h WestPartly Cloudy
2am57°F14°C15 mph23 km/h WestPartly Cloudy
3am58°F14°C16 mph26 km/h WestDrizzle
4am59°F15°C16 mph26 km/h SouthwestDrizzle
5am59°F15°C14 mph23 km/h WestDrizzle
DateLowHighWindDayNight
September 958°F15°C63°F17°C11 mph18 km/h from SouthRainRain
September 1055°F13°C64°F18°C19 mph30 km/h from SouthwestDrizzleDrizzle
September 1154°F12°C64°F18°C17 mph28 km/h from SouthwestDrizzleRain
September 1254°F12°C64°F18°C16 mph26 km/h from WestDrizzlePartly Cloudy
September 1354°F12°C67°F19°C23 mph37 km/h from SouthwestRainDrizzle
September 1457°F14°C63°F17°C29 mph46 km/h from SouthwestDrizzleWindy
September 1554°F12°C63°F17°C18 mph29 km/h from WestWindyMostly Cloudy

Yes

Low of 55°F13°C, High of 64°F18°C
Wind: 19 mph30 km/h
Precipitation: 72% rain

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