When they work outdoors they normally wear heavy clothes, covering any possible aperture, covering the head as shown in the photo. Doesn't matter if the day is not sunny, as a precaution, they cover themselves from head to toe.
Koreans as well as the Japanese, try to avoid as much as possible direct exposure to the sun. They like to keep the skin white.. Therefore, you can see very often people use umbrellas even during sunny days.
When they work outdoors they normally wear heavy clothes, covering any possible aperture, covering the head as shown in the photo. Doesn't matter if the day is not sunny, as a precaution, they cover themselves from head to toe.