So far this summer, the nationwide average number of tropical nights (days when the overnight low stays at 25 C or higher) is the highest since weather records began.
According to the Korea Meteorological Administration on the 28th, the nationwide daily average temperature from June 1 to the previous day averaged 24.2 C. Since 1973, when a nationwide weather observation system was established and became the statistical baseline, this is the second-highest for the same period.
The hottest year was last year (24.8 C), followed by the year before (24.2 C). Because weather statistics prioritize recent records, this year edged out the year before to take second place. Such a high daily average temperature means the heat did not subside and instead held steady not only during the daylight hours but also through the dark of night.
In the same period, the averages of the daily high and low were 29.1 C and 20.1 C, respectively, with both ranking fourth on record. By the same measure, the years with the highest average daytime highs were 2025 (29.8 C), 1994 (29.8 C), and 2018 (29.3 C), in that order. Periods with high average overnight lows were 2013 (20.5 C), 2025 (20.4 C), and 2022 (20.2 C), ranking first to third.
The reason the scorching heat rages day and night is a mass of hot, humid air lingering in the atmosphere. As warm, moist air continues to flow along the edge of the North Pacific High, radiative cooling at night—when the ground releases heat—has not been happening properly.
From June 1 to the previous day, the nationwide average number of tropical nights (days when the overnight low is 25 C or higher) came to 7.8 days. That is the highest for the same period since 1973.
The heat built up overnight feeds a vicious cycle that drives daytime temperatures even higher the next day. Because solar heating begins before the pre-dawn temperature has dropped enough, the starting line for daytime warming rises inevitably.
Weather experts said the peak of the heat has yet to arrive. The North Pacific High settled in the mid-to-upper atmosphere is stacked with the upper-level Tibetan High, blanketing the entire Korean Peninsula. As a result, a pattern in which hot, humid air is trapped while strong sunshine beats down is expected to persist for the time being.
The Korea Meteorological Administration forecast that from Aug. 1 to 7, morning lows nationwide will range from 23 C to 27 C, with daytime highs from 33 C to 39 C. Morning temperatures will hold near the usual range (22 C to 25 C), but daytime highs are likely to exceed the average (30 C to 33 C) by a wide margin. In particular, the agency projected that in Daegu during the first week of August, daily highs will soar to around 39 C.