Yes

you do need a jacket based on the weather in Syosset, NY 11791, USA 1 second ago

Why? Because it's cool. Pleasantly cool, but cool.
56°F13°C & Clear

Wind is 9 mph14 km/h from the NW, gusting to 17 mph28 km/h
April 24
9pm55°F13°C10 mph16 km/h NMostly Clear
10pm53°F11°C11 mph18 km/h NMostly Clear
11pm50°F10°C12 mph19 km/h NMostly Clear
April 25
12am47°F8°C13 mph20 km/h NMostly Clear
1am45°F7°C13 mph21 km/h NClear
2am42°F6°C12 mph20 km/h NClear
3am41°F5°C11 mph18 km/h NClear
4am40°F4°C10 mph17 km/h NEMostly Clear
5am38°F4°C9 mph15 km/h NEMostly Clear
6am37°F3°C9 mph15 km/h NEMostly Clear
7am38°F3°C9 mph15 km/h NEMostly Clear
8am39°F4°C10 mph17 km/h NEMostly Clear
DateLowHighWindDayNight
April 2447°F8°C69°F21°C5 mph8 km/h from WPartly CloudyMostly Clear
April 2537°F3°C55°F13°C7 mph11 km/h from EClearClear
April 2636°F2°C59°F15°C5 mph9 km/h from SEClearClear
April 2738°F3°C59°F15°C8 mph13 km/h from SPartly CloudyCloudy
April 2845°F7°C71°F21°C8 mph12 km/h from SWPartly CloudyPartly Cloudy
April 2955°F13°C83°F28°C5 mph8 km/h from SWPartly CloudyPartly Cloudy
April 3055°F13°C71°F22°C9 mph15 km/h from SEPartly CloudyDrizzle

Yes

Low of 37°F3°C, High of 55°F13°C
Wind: 7 mph11 km/h
Precipitation: None

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