A "Code Orange" air quality alert is in effect for Tuesday and could be extended further into what is forecast to be a hot and humid week.
The Maryland Department of the Environment warns that air pollution could be unhealthy for sensitive groups, such as the elderly, children and people with heart or lung conditions. Those groups are encouraged to avoid activity outdoors.
Air pollution is forecast to build over the region because of expected light winds and clear skies. Sunshine can cause chemical reactions within motor vehicle and industrial exhaust that produce ozone, a hazardous pollutant. Some smoke from wildfires in the western United States is also forecast to reach the region late Tuesday.
Mostly sunny skies and humid conditions are forecast to make highs around 90 degrees feel more like the mid-90s Tuesday.
Unhealthy air quality could continue Wednesday, though more clouds and possible storms could reduce ozone levels, according to MDE.