Record-breaking July heatwave hits South Korea once again
South Korea Experiences Record-Breaking Heat Wave and Heavy Rain in July 2025
South Korea has been grappling with an intense and prolonged heat wave since late June, leading to a surge in heat-related emergencies and fatalities. The National Fire Agency has been operating under an enhanced heat emergency response system since May 15, anticipating a sharp rise in emergency incidents caused by relentless heat.
July 2025 was the second-hottest July on record, with an average high temperature of 32°C. This extreme heat has been accompanied by the highest sea surface temperatures in the past decade, reaching an average of 24.6°C in waters surrounding the Korean Peninsula.
These record-breaking temperatures have resulted in a significant increase in heat-related illnesses. From mid-May to the end of July, 2,768 patients had visited emergency rooms for heat-related illnesses, rising to 3,306 by early August. Heat exhaustion (sunstroke) made up about 60% of cases, heat stroke 16.6%, with heat cramps and syncope making up the rest.
Vulnerable groups such as the elderly (36.6% of cases) and outdoor workers (farmers, fishermen) have been most affected. The Korea Disease Control and Prevention Agency (KDCA) has been monitoring heat illnesses since mid-May and warns of worsening heat waves.
The heat waves have caused prolonged tropical nights, including 15 consecutive tropical nights in Seogwipo (Jeju Island) and 10 consecutive tropical nights in Seoul. Emergency room visits showed a record pace, with a daily high of 238 cases reported in early July, and 58 cases reported nationwide on August 5. Deaths due to heat-related illnesses rose from 4 in the comparable period last year to over 20 by early August 2025.
In addition to the heat wave, South Korea also experienced a weeklong period of heavy rain in mid-July, causing infrastructural damage and loss of lives. The average temperatures in July 2025 were 2.5°C higher compared to the average temperatures recorded between 1991 and 2020.
The heavy rain was triggered by a series of meteorological events, including a trough carrying cold air from the northwest clashing with a stationary North Pacific high-pressure system, and a low-pressure system that evolved from a tropical depression off Jeju Island. From July 13 to July 20, 239.4 mm of the total rainfall nationwide fell during this period.
The North Pacific high-pressure system expanded above the Korean Peninsula earlier than usual, contributing to the continuation of high temperatures from late June into early July. The average low temperature in July 2025 was 23°C, making it the third highest on record. Heat wave advisories were issued for an average of 14.5 days in July 2025, which is 10.4 more days than the average from 1991-2020. In cities such as Daejeon, Seoul, and Cheongju, heat wave advisories were issued for more than half of the month in July 2025.
Projected trends for August indicate that heat waves will remain severe, with sustained high temperatures and more tropical nights expected. As a result, emergency room visits for heat-related illnesses and fatalities are likely to increase further unless mitigated by effective public health measures and behavioral changes.
[1] Korea Disease Control and Prevention Agency (KDCA) [2] National Fire Agency [3] Korea Meteorological Administration [4] Yonhap News Agency
- The intense heat wave in South Korea, as observed in July 2025, has underscored the need for more extensive environmental-science research and weather-forecasting to better counteract climate-change impact, as the Korea Disease Control and Prevention Agency (KDCA) warns of worsening heat waves.
- As South Korea grapples with record-breaking heat waves and heavy rain, it's crucial to integrate climate-change considerations into weather-forecasting models, given the observed link between extreme weather events and rising temperatures, as reported by the National Fire Agency and Korea Meteorological Administration.
