The Maryland Department of the Environment has issued an air quality advisory for June 20, the first day of summer.
On top of the , officials forecast an air quality index (AQI) of 106-in the "orange" or "Unhealthy for Sensitive Groups" range because of high levels of ozone.
On Wednesday and Thursday, hot and humid conditions with light, west-northwesterly winds will cause ozone and fine particle levels to rise, according to MDE. Fine particles are expected to remain in the Moderate AQI range, officials said.
A cold front is forecast to roll into the region on Friday, which may produce cloud cover and thunderstorms. A Moderate AQI is expected to result after the front passes through later in the day on Friday, according to MDE.
Updated air quality information and forecasts are available through MDE's Air Quality Hotline at 410-537-3247.
High temperatures and poor air quality can be especially unhealthy for the elderly. Montgomery County on Wednesday issued tips for coping with the high temperatures.
The City of Rockville offering a free place to stay out of the heat.