South Korea logged its highest-ever temperature of 40.3 C on Wednesday as a sweltering heat wave continued to grip wide areas of South Korea, weather authorities said.

The mercury hit the record high at an observatory in Hongcheon, a town in South Korea's northeastern province of Gangwon, at 2:20 p.m., marking the highest level since 1907, when the country began to compile the data, the Korea Meteorological Administration (KMA) said.

In Seoul, the temperature was recorded at 38.8 C at the same time.

It marked the second time for the country's temperature to soar above the 40 C threshold following a reading of 40 C in the southeastern city of Daegu on Aug. 1 in 1942.

On July 27 this year, 39.9 C was recorded at Chupung Pass in the central province of North Chungcheong and in the southeastern town of Uiseong.

Seoul recorded a previous record high temperature of 38.4 C on July 24, 1994, while temperatures of 38.3 C on Tuesday, and 38.2 C on both Aug. 24, 1943, and July 23, 1994, were also recorded in the capital.

The country has been hit by a long-running heat wave nationwide following the rainy season, with a lack of rainfall coupled with high atmospheric pressure from Tibet attributing to the heat wave.

Another factor is easterly winds that blow from the Taebaek Mountains in South Korea's eastern area. Warm air flowing down from the mountains pushed up temperatures in Seoul. This condition is known as a dry foehn.

It is highly likely that the record-high temperatures of the country and Seoul will rise during the same day as the country is experiencing its hottest summer day. (Yonhap)