South Korea's air quality reached the worst level this winter Saturday due to high levels of fine dust and yellow dust, according to weather authorities.

As of 10 a.m., the daily average concentration of ultrafine dust particles smaller than 2.5 micrometers in diameter, known as PM2.5, was 86 micrograms per cubic meter, while that of fine dust known as PM10 was 143 micrograms per cubic meter across the country, according to Air Korea run by the environment ministry.

The figures were much higher than the yearly average concentration of ultrafine and fine dust of 18 and 36 micrograms per cubic meter, respectively, in 2021.

The weather authorities have issued an ultrafine dust advisory in all areas except for the southern resort island of Jeju, and a fine dust advisory in Gyeonggi Province, which surrounds Seoul, the central Chungcheong provinces, and the South Jeolla and South Gyeongsang provinces.

As of 5 p.m. Friday, a yellow dust warning has been in effect in South Chungcheong Province, the Jeolla provinces, the southwestern city of Gwangju and Jeju Island.

On Sunday, the fine dust level is also expected to be "bad" across most parts of the nation, including the greater Seoul area and the eastern Gangwon Province.

The Korea Meteorological Administration categorizes concentrations of fine dust between 81 and 150 micrograms as "bad" and more than 151 as "very bad."

Authorities advise people to refrain from leaving their homes on such days and wear a face mask if they have to go outside. (Yonhap)