Is Jeju Island hot at the end of June?

I went to Jeju at the end of May last year. If the weather is fine, just wear a T-shirt during the day. It's windy by the sea, so wearing a thin coat won't get hot. Because it is an island, the temperature drops rapidly after sunset. If it's a little cold in the morning and evening, just bring a coat. Jeju generally has good air, so it has strong ultraviolet rays. Pay attention to sun protection.