A Code Orange Air Quality Alert will be in effect through Thursday evening for the Tri-Cities, Knoxville and Chattanooga metro areas, as well as in the Smoky Mountains.

Air Quality Alert Thursday Map
WBIR Weather

Ground-level ozone concentrations will be elevated and may reach unhealthy levels for groups with sensitive respiratory systems.

Folks that fall into that  "sensitive" category should avoid extended periods of time outdoors or strenuous outdoor activities.

Code Orange Air Quality Alert
WBIR Weather

When we have sunny days, hot temperatures and light winds, ground-level ozone concentrations can become elevated as the sunlight and heat interact with pollution in the emissions from cars. 

According to the Environmental Protection Agency, the sun's direct ultraviolet rays convert these emissions into ground-level ozone, which is unhealthy to breathe for folks that have Asthma and other respiratory issues.

This elevated level of ozone will likely not affect the general population.