Seoul City has seen a threefold increase on-year in the number of serious heat-related illnesses this summer, authorities said Friday.

According to the Seoul Metropolitan Fire and Disaster Management Headquarters, a total of 158 cases were reported through 911 emergency calls between May 15 and Aug. 31.

This year's figure is approximately three times larger than the 50 cases recorded last year.

Of those patients, 104 were diagnosed with heat exhaustion, followed by 24 cases of heat stroke and 15 cases of heat syncope. Another 14 individuals showed symptoms of heat cramps, and one suspected patient's condition remained uncategorized in the fire station's report.

Out of these cases, 114 suspected patients were transported to emergency rooms, while 44 patients received immediate emergency treatment at the scene. Among the different age groups, individuals in their 60s accounted for the majority, comprising 57 percent with 90 cases.

The highest number of heat-related incidents occurred in August, with 97 reported cases. This was followed by July, which had 48 cases, and June, which saw 13 cases.

Over the course of these three months, the fire authorities conducted 4,632 patrols as part of their disaster relief operations and carried out 3,493 searches in areas vulnerable to heat-related issues.

An official from the fire headquarters attributed this year’s surge in heat-related ailments to sweltering heat caused by global warming, urging “people and workers to avoid outdoor activities and field work during heat wave advisories.”