Jacket + shirt. Dongying in May is already not cold, the daytime temperature is about 20 ℃, but at night the temperature drops down to about 10 ℃, so it is necessary to wear a jacket + shirt. May Day is the International Labor Day. International Labor Day, also known as "May Day International Labor Day" "International Day of Demonstrations" (English: International Workers' Day, May Day), is a national holiday in more than 80 countries in the world.