Explain the bad weather in Baotou with professional knowledge.

Baotou is actually a good city, probably because it is deeply affected by environmental deterioration, and the local government also attaches great importance to greening. Almost every community has a small forest or square, about 10 minutes away. Summer is not hot, and July and August are the most comfortable seasons every year. But in March and April of the following year, there will be sandstorms when the wind blows. Above the height of 20 floors, only the sky is gray and the visibility is very low. Usually you can see the mountains in the northwest when the weather is good, but you can't see the mountains when the weather is a little cloudy. It takes half an hour by car in Baotou to reach the famous desert scenic spot Xiangshawan, so the bad weather should be related to the surrounding desert. Also, Baotou is located in the west, and the local people think that the exhaust gas from Baotou just covers the whole Baotou when the wind blows ... In short, no matter what the weather is, the local people are used to wearing masks when they go out.