South Korea experienced three to four more days of heat waves and tropical nights per year during the past decade than it did during the past 48 years, data from the Korea Meteorological Administration showed Monday.

Heat wave days from 2011 to 2020 averaged 14 days per year, up 3.9 days from the 10.1 days recorded between 1973 and 2020. The average number of tropical nights increased 3.3 days to nine days during the same period.

A heat wave alert is issued when the maximum sensible temperature exceeds 33 C for more than two consecutive days or the hot weather is expected to cause major damage.

A tropical night occurs when the temperature does not fall under 25 C during the nighttime.

By region, heat wave days have been most frequent in southeastern regions during the past 10 years, including Daegu (27.6 days), Hapcheon (24.3 days) and Miryang (22.8 days), the data showed.

The southern island of Jeju was hit by the most tropical nights during the period, including Seogwipo (31 days) and Jeju City (29.9 days).

2018 observed the most heat wave days of 31 and the second most tropical nights of 16.6. (Yonhap)