The temperature of the earth surface in those areas fell down to 3-2 degrees centigrade below zero, whereas the temperature at the height of 700 meters from the ground level rose 2-3 degrees centigrade. As a result, the temperature inversion was formed and the atmospheric humidity got very high, creating thick fog.

In particular, most areas of Pyongyang City and Unsan County of South Phyongan Province, Sungho County of North Hwanghae Province and Kangso District of Nampho City witnessed three consecutive days of thick fog with visibility distance of less than 100 meters and high density of fine dust that affected the health and activity of people and the movement of transport means.

According to weather experts, this phenomenon is an unprecedented one in the country's meteorological observation history.