Wildfire smoke is spreading across a wide stretch of the eastern United States, with forecasters warning that conditions in the Northeast and Mid-Atlantic are likely to deteriorate through Friday. The haze has already affected areas from the Midwest eastward, turning air quality into a growing health concern.

More than 115 million people could be exposed to unhealthy air as smoke lingers and thickens in some locations. The broad reach of the pollution means major population centers may continue to see reduced visibility and worsening breathing conditions over the next several days.

The outlook points to the most serious impacts in parts of the Northeast and Mid-Atlantic, where smoke levels are expected to remain elevated or increase before improving. Forecast coverage for 20 cities underscores how widespread the event has become and how many communities may face changing conditions from one day to the next.

Officials typically urge residents to pay close attention to local air quality updates during smoke events, especially people with respiratory conditions, older adults, and children. As the smoke shifts across the region, the biggest concern remains the prolonged period of unhealthy air stretching into the end of the week.