Yes

you do need a jacket based on the weather in Bethesda, MD, USA 1 second ago

Why? Because it's cold. simple as that.
42°F5°C & Mostly Clear

Wind is 5 mph8 km/h from the W, gusting to 14 mph22 km/h
March 29
9am42°F6°C6 mph9 km/h WMostly Clear
10am46°F8°C7 mph12 km/h WMostly Clear
11am50°F10°C11 mph17 km/h NWPartly Cloudy
12pm53°F12°C13 mph21 km/h NWMostly Clear
1pm56°F13°C14 mph23 km/h NWMostly Clear
2pm58°F14°C16 mph25 km/h NWWindy
3pm59°F15°C16 mph26 km/h NWWindy
4pm59°F15°C16 mph26 km/h NWWindy
5pm59°F15°C16 mph25 km/h NWWindy
6pm57°F14°C14 mph22 km/h NWClear
7pm54°F12°C11 mph17 km/h NWClear
8pm51°F11°C8 mph12 km/h NWClear
DateLowHighWindDayNight
March 2936°F2°C59°F15°C12 mph19 km/h from NWMostly ClearClear
March 3037°F3°C62°F17°C5 mph9 km/h from SWMostly CloudyPartly Cloudy
March 3150°F10°C68°F20°C6 mph10 km/h from NWMostly CloudyRain
April 148°F9°C57°F14°C7 mph12 km/h from ERainRain
April 246°F8°C58°F14°C6 mph9 km/h from ERainRain
April 343°F6°C57°F14°C9 mph15 km/h from NWRainDrizzle
April 440°F4°C50°F10°C16 mph25 km/h from NWWindyPartly Cloudy

Yes

Low of 37°F3°C, High of 62°F17°C
Wind: 5 mph9 km/h
Precipitation: 23% rain

Support This Page