CHICAGO (Fox 32 News) - Many people in the Chicago area wondered why Friday night's rainstorm seemed to be "dirty."
Fox 32 News Meteorologist Mike Caplan was flooded with photos of cars that seemed to be covered in little gray spots.
Caplan explained that the sky is always full of dust, and that dust is a critical part of cloud building.
"Sometimes though, especially when it has been dry and windy ahead of the rain, more dust and dirt gets picked up into the air," Caplan said. "When those particulates come into contact with the falling rain, they cling to it. After the rain evaporates, all that’s left is the solid residue."