Most of Maryland, including Montgomery County, is under an “Unhealthy for Sensitive Groups” (USG) air quality alert as wildfire smoke combines with elevated ozone levels during a stretch of above-normal temperatures. At the same time, a Heat Advisory remains in effect until 8pm Thursday.
The National Weather Service says heat index values could reach around 105 degrees across Washington, D.C., much of Maryland, and northern Virginia. The combination of high temperatures and humidity could lead to heat-related illnesses, especially for those spending extended periods outdoors.
According to the Maryland Department of the Environment (MDE), a multi-day air quality event is expected to continue through at least Friday and could linger into Saturday. A wave of wildfire smoke is forecast to move into central Maryland Thursday morning, bringing elevated levels of fine particle pollution, particularly along the Interstate 95 corridor. Northeastern Maryland is expected to experience the highest concentrations of smoke because it will arrive there first and remain the longest.
At the same time, ozone pollution is expected to increase statewide due to the combination of intense heat and aging wildfire smoke. While most areas are forecast to experience “Unhealthy for Sensitive Groups” ozone levels, some locations downwind of Baltimore over the Chesapeake Bay could briefly approach the “Unhealthy” category.
Conditions are expected to worsen on Friday as a weak cold front pushes additional wildfire smoke into Maryland. Light, recirculating winds are forecast to keep the smoke in place throughout the day, leading MDE to forecast Code Red (“Unhealthy”) air quality for fine particle pollution statewide. Ozone levels are also expected to remain elevated, provided enough sunlight reaches the ground.
Rain chances increase on Saturday, which could improve air quality by reducing ozone levels and washing some of the smoke from the atmosphere. However, MDE says it remains uncertain whether rainfall will be sufficient to completely end the air quality event. While Moderate air quality is currently forecast for Saturday, conditions could still reach the “Unhealthy for Sensitive Groups” category.
Officials encourage people to limit strenuous outdoor activity during the hottest part of the day and to stay hydrated. Children, older adults, and those with heart or lung conditions should also reduce prolonged outdoor exposure while air quality remains poor, as they are most vulnerable to the combined impacts of extreme heat and wildfire smoke.
