Why did the plane from Dalian to Xuzhou stop?

weather Dalian Airport has announced that the flight from Dalian to Xuzhou will be suspended due to foggy weather, so it can be changed or refunded due to the weather. Dalian, also known as Bincheng and Romantic City, is a prefecture-level city, a sub-provincial city, a city with separate plans and a megacity under the jurisdiction of Liaoning Province, and is an important central city in the northern coastal area of China as determined by the State Council.