Temperatures are expected to shoot up to 37 C in the city of Goyang, north of Seoul, on Wednesday, as a heat wave grips the nation, the state weather agency said.

Other parts of the country are also expected to see temperatures rise to 35 C or higher. Highs are forecast to be 36 C in the southeastern city of Daegu and 35 C in Seoul, the central city of Daejeon and the southwestern city of Gwangju, the Korea Meteorological Administration said.

The eastern coastal city of Gangneung was hit by yet another tropical night, in which the lowest temperature stays above 25 C overnight. It marks the third tropical night for the city following two occasions last week.

The season's first heat wave advisory was issued for Seoul as of 10 a.m., leaving all of the greater Seoul area, excluding Incheon, under the advisory.

A heat wave advisory is issued when the highest apparent temperature is expected to be 33 C or higher for two or more consecutive days. It is also issued when significant damage is expected due to a sudden increase in apparent temperatures or prolonged heat wave conditions.

The advisory took effect in 92 regions in total across the country, with the KMA pointing to the influence of high atmospheric pressure and the warm westerly wind in bringing up temperatures higher compared to average years.

While the heat wave will continue to affect the central regions, thick clouds and rainfall will lower temperatures in the southern regions and the southern island of Jeju on Thursday.

On Jeju, monsoon rain will start pouring later in the day, and it is expected to continue until Friday morning. The island will receive between 50 and 100 millimeters of rain, according to the KMA.