Why is it that smog more common in summer?
Smog is smoky fog. In cities, the air contains many extra particles because of the smoke released by some of the industries. Water vapor condenses on these to form smog. In summer this is worsened by an effect called an inversion – a layer of warm air prevents the surface air, and the pollutants it contains, from rising. This can also happen in regions where air is trapped by surrounding mountains, such as Los Angeles, California.