July sets record for most tropical nights ever

Daytime lows in July noted as second highest on record

Local residents sleep overnight on Gyeongpo Beach in Gangneung, Gangwon Province, Wednesday, to escape the persistent tropical night that has lasted for 19 days in the city. (Yonhap)

This July experienced the highest number of tropical nights for any July since weather records began in 1973, the Korea Meteorological Administration said last month.

South Korea recorded an average of 8.8 tropical nights this July, a three-fold increase compared to the previous average of 2.8 days in past Julys, according to the KMA's monthly weather analysis report.

Tropical nights refer to a phenomenon where the lowest temperature remains above 25 degrees Celsius between 6:01 p.m. the night before and 9 a.m. the next day.

Some cities such as Gangneung in Gangwon Province and Pohang in North Gyeongsang Province saw tropical nights occur for more than half of July, with 17 nights recorded.

As of Wednesday, Gangneung has seen 19 consecutive tropical nights since July 19, the longest number of tropical nights recorded in the city in 113 years. Pohang, on the other hand, has seen 13 consecutive tropical nights since July 25.

The average lowest daytime temperature recorded in July was 23.3 C, an increase of 2.1 C compared to previous Julys. This was the second highest on record for average daytime low temperatures, just 0.1 C lower than the highest record set in 1994.

Regarding the reason behind high daytime low temperatures and frequent tropical nights, the KMA pointed toward the North Pacific anticyclone.

According to the weather agency, the North Pacific anticyclone extended further northwest compared to previous years, bringing hot and humid southwesterly winds more frequently than normal.

Though the monsoon season that lingered early and mid-July prevented daytime temperatures from significantly increasing, hot air containing a heavy amount of water vapor was brought in by southwesterly winds, which kept temperatures from dropping overnight.

Additionally, the convergence of the Tibetan and North Pacific anticyclones fueled the intense heat waves that covered most of Korea after the monsoon season ended.

From July 27 to 31, the KMA noted that three cities, Gangneung and Sokcho in Gangwon Province and Miryang in South Gyeongsang Province, experienced the highest average daytime temperatures on record this year, reaching up to 30.4 C, 30.3 C and 28.1 C respectively.

Korea also saw precipitation recording up to 383.6 millimeters in July -- the 10th highest on record and more than average precipitation amounts from previous years, which range from 245.9 mm to 308.2 mm.

By Lee Jung-joo(lee.jungjoo@heraldcorp.com)