The number of fatalities from the ongoing heat wave in the country has climbed to 13, after five more people died over the weekend.

According to the Korea Disease Control and Prevention Agency(KDCA) and fire authorities on Monday, five people are presumed to have died from heat-related illnesses during the weekend.

Heat-related illness refers to acute conditions that develop due to high temperatures, with symptoms such as headache, dizziness, muscle cramps, and fatigue after prolonged exposure to heat.

There have been one-thousand-546 recorded patients, including deaths, this summer season through Saturday, of which 31-point-four percent were seniors aged 65 or older.

Seniors tend to be more vulnerable to heat-related conditions as aging weakens their ability to sense rising body temperatures and symptoms of dehydration, as well as their ability to regulate body temperature and control sweating.