Children splash in a fountain in front of the Kim Dae-jung Convention Center in Gwangju at the end of July when the rainy season was over and the heat wave beginning.

The nation saw more sleepless "tropical nights" this summer than ever, when nighttime temperatures stayed above 25 degrees Celsius. There were twice as many of them this summer as in the average year. In August alone, the frequency of tropical nights was four times higher than ever before. Meteorologists cite global warming and the "heat island" effect as the main culprits.

According to a Korea Meteorological Administration report on the summer weather this year released Monday, the average temperature this August was 26.1 degrees Celsius in 60 areas nationwide, up 1.1 degrees from the 35-year average of 25 degrees. Average daily highs rose 0.8 degrees to 30.4 degrees, while the average daily lows rose 1.6 degrees to a 35-year record of 22.9 degrees.

The surge in the daily low increased the number of tropical nights to 11 days in Seoul in August, four times more than before. Other cities like Daegu, Gangneung and Jeonju suffered from a similar frequency of tropical nights. The KMA said during the three months of summer this year, most parts of Korea experienced twice as many tropical nights as in the past.

Rainfall was 676.3 mm this summer, 23.6 mm less than before, but Korea saw 46 days of rain this summer, seven days more than in the past. Prof. Ha Kyung-ja of Pusan National University's Department of Atmospheric Sciences said the frequent rains prove that global warning "is well underway."