Yes

you do need a jacket based on the weather in Merthyr Tydfil, UK 1 second ago

Why? Because it's pretty chilly.
59°F15°C & Mostly Cloudy

Wind is 6 mph9 km/h from the NE, gusting to 14 mph22 km/h
May 6
8am60°F15°C6 mph10 km/h NEMostly Cloudy
9am61°F16°C6 mph10 km/h NMostly Cloudy
10am62°F16°C7 mph11 km/h NMostly Cloudy
11am62°F17°C7 mph11 km/h NDrizzle
12pm61°F16°C7 mph11 km/h NPartly Cloudy
1pm60°F16°C8 mph12 km/h NPartly Cloudy
2pm59°F15°C7 mph12 km/h NPartly Cloudy
3pm57°F14°C7 mph10 km/h NPartly Cloudy
4pm55°F13°C6 mph10 km/h NMostly Clear
5pm53°F12°C6 mph9 km/h NMostly Clear
6pm51°F11°C5 mph8 km/h NMostly Clear
7pm50°F10°C5 mph7 km/h NClear
DateLowHighWindDayNight
May 544°F7°C62°F17°C6 mph9 km/h from NDrizzleMostly Clear
May 646°F8°C64°F18°C3 mph5 km/h from NWMostly CloudyMostly Cloudy
May 748°F9°C65°F18°C6 mph9 km/h from SWMostly CloudyMostly Cloudy
May 848°F9°C67°F20°C3 mph5 km/h from WMostly CloudyCloudy
May 951°F11°C69°F21°C4 mph7 km/h from SMostly CloudyPartly Cloudy
May 1051°F11°C69°F21°C7 mph11 km/h from SEPartly CloudyPartly Cloudy
May 1151°F11°C68°F20°C8 mph13 km/h from SMostly CloudyMostly Cloudy

Yes

Low of 46°F8°C, High of 64°F18°C
Wind: 3 mph5 km/h
Precipitation: 9% rain

Support This Page