As South Korea faces its most extreme summer rainfall season in decades, new data shows dangerous downpours are no longer rare.
According to the Korea Meteorological Administration, there were 31 instances in the summer of 2024 where rainfall exceeded 80 millimeters in a single hour. That is nearly four times the number recorded in 2015, when just 8 such events occurred.
While the yearly totals have fluctuated over the past decade, the KMA reports a clear overall increase. The agency also noted that powerful rainfall is now appearing even after the country’s typical monsoon season ends in August, with more frequent bursts exceeding 50 millimeters per hour.
By the KMA’s definition, “extreme rainfall” is when one hour brings at least 50 millimeters of rain and three hours bring 90 millimeters or more, or when one hour alone sees 72 millimeters or more.
This past week shattered those standards. Between July 17 and 20, at least 10 regions recorded daily rainfall the agency says statistically "occurs once every 200 years." Incheon’s Ongjin-gun and Gyeonggi’s Pocheon saw rare one-hour extremes, while Seosan, South Chungcheong Province, and Gwangju set new national daily records with over 426 millimeters of rain each.
KMA meteorologists said the underlying cause is a collision of two very different air masses. Dry, cold air lingered unusually far south over the Korean Peninsula, while warm, moisture-heavy air from the Pacific surged in from the south. The two clashed and stalled, creating a volatile zone where storm clouds continued to form in the same locations.
That weather pattern is now shifting. The Pacific high-pressure system is expanding, locking in hot and humid air and setting the stage for prolonged heat waves.
mjh@heraldcorp.com
