Yes

you do need a jacket based on the weather in Lusk, WY 82225, USA 1 second ago

Why? Because it's pretty chilly.
52°F11°C & Clear

Wind is 4 mph7 km/h from the SW, gusting to 7 mph12 km/h
September 20
5am52°F11°C5 mph7 km/h SWClear
6am51°F11°C5 mph8 km/h SWClear
7am51°F10°C6 mph9 km/h SWClear
8am50°F10°C6 mph9 km/h SWClear
9am51°F11°C6 mph10 km/h SWClear
10am56°F14°C6 mph10 km/h SWClear
11am64°F18°C7 mph12 km/h SWClear
12pm70°F21°C10 mph17 km/h SWClear
1pm74°F23°C11 mph18 km/h SWClear
2pm77°F25°C11 mph18 km/h WClear
3pm79°F26°C11 mph17 km/h WClear
4pm80°F27°C10 mph16 km/h WClear
DateLowHighWindDayNight
September 2050°F10°C81°F27°C10 mph16 km/h from WClearClear
September 2145°F7°C65°F18°C16 mph26 km/h from NWindyMostly Cloudy
September 2239°F4°C65°F18°C11 mph17 km/h from SPartly CloudyClear
September 2344°F7°C68°F20°C13 mph21 km/h from NWMostly CloudyPartly Cloudy
September 2442°F6°C66°F19°C11 mph17 km/h from NWPartly CloudyClear
September 2542°F5°C74°F23°C7 mph11 km/h from SClearClear
September 2649°F9°C79°F26°C10 mph16 km/h from WClearClear

Yes

Low of 46°F8°C, High of 65°F19°C
Wind: 16 mph26 km/h
Precipitation: None

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