High levels of ultrafine dust are forecast for most of the country on Wednesday.

The National Institute of Environmental Research forecast ultrafine dust level of "bad," or from 36 to 75 micrograms per cubic meter, between Tuesday night and Wednesday nationwide, except for the eastern part of Gangwon Province and the southernmost Jeju Island.

Ultrafine dust level of "very bad," or at least 76 micrograms per cubic meter, is forecast for the capital region and the central city of Sejong through early Wednesday.

Amid cloudy skies, rain or snow could be observed in the capital area and in the northern inland regions of Gangwon Province until early hours of Wednesday.

Morning lows nationwide are expected to range between minus six and three degrees Celsius above freezing, while daytime highs are projected to rise to between four and 13 degrees.