Why do smog weather often occur in spring and summer?

(1) Heating in spring and winter significantly increases particulate emissions from coal combustion.

(2) The dust phenomenon caused by ground exposure in spring and winter is more serious than that in summer.

(3) Meteorological conditions in spring and winter are not conducive to the diffusion of particulate matter, such as inversion of temperature often leads to extreme pollution.

(4) The temperature is low in spring and winter, and some gaseous pollutants are easy to condense into small particles.