State forecasters expect potentially unhealthy levels of air pollution in the Charlotte area on Thursday.
The Code Orange alert is for ozone, a transparent gas that can worsen asthma and other breathing conditions. Children, seniors and people who are active outdoors are also at risk.
Those people should limit their physical exertion outdoors Thursday afternoon, when ozone levels are expected to be highest.
Ozone forms on hot, stagnant days from emissions that come from motor vehicles, power plants and industries.
The forecast predicts that ozone levels in Charlotte and the Greensboro area will exceed the federal standard of 70 parts per billion averaged over eight hours. Ozone levels in the Charlotte area have exceeded that standard once this year, on May 16.
The Division of Air Quality issues daily air forecasts for the Asheville, Charlotte, Hickory, Fayetteville, Rocky Mount and Triangle metropolitan areas.