Seoul experienced 10 consecutive tropical nights, though the nighttime temperature cooled somewhat in recent days, the state weather agency said Friday.

Seoul, other large cities, some coastal areas and Jeju Island saw their temperatures stay above 25 C between Thursday night and Friday morning, according to the Korea Meteorological Administration (KMA).

A tropical night occurs when the temperature does not fall below 25 C during the nighttime.

The minimum temperature overnight was 25.8 C in Seoul, 25.9 C in Incheon, west of Seoul, 25.1 C in the southeastern coastal city of Busan and 25.7 C on southern Jeju Island. Seoul's nighttime low was down slightly from over 27 C recorded in recent days.

That means Seoul experienced 10 straight tropical nights, along with 13 in Incheon, and 12 on Jeju.

In July, Seoul and Busan both experienced the phenomenon for a total of 15 nights, while Jeju had 23 such nights and Incheon 17.

The KMA said heat wave alerts have been issued for most of the country Friday, with the daytime temperature expected to hover around 35 C.

It advised workers vulnerable to heat, such as farmers, fishers and medical personnel working outside amid the COVID-19 pandemic, to take precautionary measures to prevent harm from sweltering weather.

It is best to not work between midday and 5 p.m. and stay hydrated and saline, the KMA explained. (Yonhap)