As a record-smashing heat wave continues, more patients are suffering from heat-related diseases, according to the Korea Centers for Disease Control and Prevention on Thursday.

There were 1,487 patients of heat-related illnesses from May 20 to July 24, a 78 percent increase from last year during the period of May 29 to July 26 of 833 patients, reported KCDC.

Although 60 percent of the patients were in their 50s or older, 36 percent, or 541 people, were in their 20s to 40s. Health experts have cautioned young people to be careful, as the heat causes blood flow to increase to the heart, leading some people to faint.

Seventeen people have died from the heat this year.

Seoul National University Hospital professor Park Min-sun from the pediatric department said that many young people are not aware of the limits of their body. Park advised young office workers to be careful to not overdrink or eat too much late at night, as such behavior could lead to fatigue.

The nation had its hottest morning in 111 years on Monday of 31 degrees Celsius in Gangneung, Gangwon Province, which marked the highest temperature since modern meteorological observation started in 1907, according to the Korea Meteorological Administration.

Korea may see the hottest summer on record, as daytime temperatures may exceed 40 C, according to the weather agency. Daegu is so far the only city in Korea to hit 40 degrees during the daytime, on Aug. 1, 1942.

By Chyung Eun-ju (ejchyung@heraldcorp.com)