A Code Orange Air Quality Action Day has been issued by the Pennsylvania Department of Environmental Protection (DEP) for Wednesday, June 30th. The alert covers the southeastern counties of Bucks, Chester, Delaware, Montgomery, and Philadelphia.

According to the notice, the alert was issued due to a forecast of a mix of partly sunny skies, high temperatures in the middle 90s, and limited chances for any afternoon thunderstorms. These conditions are predicted to contribute to an eight-hour average concentration of ozone in the Code Orange range on Wednesday.

The U.S. Environmental Protection Agency’s (EPA) Air Quality Index (AQI) provides standardized color codes for forecasting and reporting daily air quality. Green signifies good air quality; Yellow means moderate air quality; Orange represents unhealthy pollution levels for sensitive groups of people; and Red warns of unhealthy pollution levels for all.

An Air Quality Action Day is issued when the AQI is forecasted to be Code Orange or higher. On an Air Quality Action Day, young children, the elderly, and those with respiratory problems, such as asthma, emphysema, and bronchitis, are especially vulnerable to the effects of air pollution and should limit outdoor activities.