South Korea's weather agency on Thursday issued a strong wind advisory for the entire nation, calling for concerted preparedness for typhoon-class winds and forest fires throughout the day.

The Korea Meteorological Administration (KMA) said wind gusts of up to 90 kilometers per hour, or 25 meters per second, will blow across the nation, due to the difference in air pressure between cold low pressure over North Korea and warm high pressure southeast of the peninsula.

The KMA put the entire nation under a high wind advisory as of 9 a.m., as mountain fires, apparently fanned by the unseasonably strong winds, broke out in Seoul and Gangwon Province, east of the capital, early in the morning.

The agency said it will upgrade its strong wind advisory to a strong wind warning in the Seoul metropolitan area at noon, adding the warning could be expanded to other regions.

A strong wind warning is issued when the land wind speed is expected to exceed 21 meters per second or the instantaneous maximum wind speed is forecast to top 26 meters per second.

It will be the first time since the KMA began relevant record-keeping in 1999 that Seoul has been put under a strong wind warning.

In particular, KMA officials urged hospitals and clinics nationwide to ensure that their makeshift tents and other outdoor medical facilities set up to handle suspected and confirmed patients of the coronavirus are not damaged by the strong winds.

It was the first time in nearly one year that a high wind advisory was issued under the influence of low atmospheric pressure in the nation.

The agency noted a maximum wind speed of 32.1 meters per second was recorded in Yangju, north of Seoul, as of 9 a.m., while Mount Seorak near the east coast and Incheon, west of the capital, logged per-second wind speeds of 29.4 meters and 24.3 meters, respectively.

In Seoul, the instantaneous maximum wind speed reached 13.2 meters per second.

"Winds will grow gradually stronger, reaching the maximum speeds between noon and 9 p.m. As the atmosphere is very unstable, whirlpool gusts are also expected," a KMA official said.

He called for extraordinary countermeasures to secure the safety of makeshift hospital tents related to COVID-19, church spires, storefront signs, walls, greenhouses and other outdoor facilities, while asking people to stay indoors throughout the day.

The KMA also cautioned against forest fires, saying small embers could lead to big fires, particularly in eastern coastal and inland areas, due to the dry atmosphere.

Around 3:30 a.m., a fire broke out on Mount Surak in Seoul's northern ward of Nowon, burning about 660 square meters of forest.

About 1,500 firefighters and civil servants were mobilized to the scene and put out the fire five hours later. No casualties were reported, and firefighters began their investigation into its cause.

Another forest fire, apparently related to the ongoing strong winds, was reported in Wonju, about 130 km east of Seoul in Gangwon Province, around 7 a.m., though it was extinguished in two hours and caused no casualties. (Yonhap)