It's fairly common for dust to be picked up by wind storms as they cross the Sahara Desert in Africa. That dust gets lofted into the atmosphere and remains suspended high above the ground by strong upper level trade winds.
These winds are so strong, they can blow the dust across the Atlantic Ocean - and sometimes, it reaches the U.S. In these cases, a layer of dust can be found on cars mainly in southern states, like Florida and Texas. It can also impact those with breathing issues.
Forecasters are calling for the African dust to reach the Chicago area on Sunday into Monday. With rain in the forecast on Sunday, it probably won't be too noticeable - but the sky may look hazier than usual.