(ATTN: CHANGES headline; ADDS more info on heatstroke index, casualties in paras 4-10)
SEOUL, July 25 (Yonhap) -- South Korea's weather authorities issued a heat wave advisory for Seoul Wednesday in response to predictions that the mercury will rise to 33 C in the afternoon.
The advisory is the first to be issued for the capital city this year, and is given when temperatures are likely to stay above 33 C for two consecutive days in the June-September period.
Seoul's temperature is expected to reach a high of 34 C on Thursday.
Along with the continued scorching weather nationwide, with the daytime high in the southeastern city of Daegu expected to soar to 37 C, stress is expected to reach a dangerous level for people, ringing an alarm bell in maintaining public health.
According to the data by Kweather, the country's private weather service provider, the Wet Bulb Globe Temperature (WBGT) index is expected to reach as high as 30 C around 3 p.m. on Wednesday in Daegu, Pohang and Gwangju, followed by 29 C in Daejeon and several cities in the central region, and 28 C in Seoul and Busan.
The WBGT index, one of the most widely-used gauges to assess heat stress, is a composite temperature to estimate the effect of the actual temperature, humidity, wind speed and radiant heat on people. A reading between 28 C and 31 C is classified as "dangerous," with over 31 C being regarded as "very dangerous."
At the "dangerous" level, people are advised to refrain from vigorous workouts and to drink enough water, and stopping exercise altogether is highly recommended at the "very dangerous" level, according to the Korea Centers for Disease Control and Prevention (KCDC).
The level is likely to reach as high as 31 C on Thursday afternoon, according to the forecast.
"The number of patients suffering from heat-related illness has been on the rise," a KCDC official said, adding one person has been confirmed dead and some 110 patients have visited a doctor due to the sweltering heat since June when the summer season began.
An elderly couple found dead late Tuesday in a greenhouse in North Gyeongsang Province might have also died of heatstroke, according to police. The couple's skin was severely tanned and there were no signs of foul play, though the exact cause of death is still under investigation, police said.
"Outdoor activities are discouraged due to possible ill effects of hot weather and there is a need to drink lots of water to prevent overheating and dehydration," the Korea Meteorological Administration said.
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