Hottest July on Record: South Korea Sees Longest Tropical Nights, Highest Minimum Temperatures

South Korea endured its hottest July on record this year, marked by the highest average minimum temperature and the most tropical nights ever recorded. This intense heatwave, which began in early July, has set a new benchmark for extreme weather in the country.

The national average temperature for July was 26.8 degrees Celsius, making it the third hottest July since records began. The latter half of the month saw a significant expansion of the subtropical high-pressure system from the southeast, causing temperatures to soar, particularly in the Gyeongnam region. Daily high temperatures in Gyeongnam recorded new records for four consecutive days from July 28 to 31. This phenomenon was amplified by high-altitude, dry air from the Tibetan Plateau and the "Föhn effect," where winds blowing over mountains heat up the land.

Crucially, the average minimum temperature reached 23.4 degrees Celsius, the highest on record. Tropical nights, where temperatures do not drop below 25 degrees Celsius, occurred on 9.7 days on average nationwide, far exceeding the annual average of 2.8 days and surpassing the previous record of 8.8 days in 2024. This phenomenon is attributed to the inflow of hot and humid air from the southwest, weakening the cooling effect of radiation at night. Western regions, the southern coast, Jeju Island, and major cities experienced over 10 days of tropical nights, with 17 locations recording their highest number of tropical nights ever.

A key characteristic of July's climate was the stark regional polarization. Despite being the monsoon season, the stationary front primarily brought rain to the central regions, creating a narrow band of precipitation. Nationwide, July rainfall was 220 millimeters, only 72.3% of the annual average. Gyeongnam received a mere 68 millimeters, just 21% of its average, making it the driest July on record. This contrast allowed the Gyeongnam region, already under the influence of the subtropical high, to experience an early and prolonged heatwave. Additionally, warmer sea surface temperatures in the Yellow Sea and South Sea in late July contributed to the heat, with temperatures ranking third highest in the past decade.