Some background on what's happening from AccuWeather:
After a smoky sunset Monday evening, heavy smoke continued to hang over the Northeast on Tuesday, as a result of more than 100 wildfires burning in the western U.S. and more in Canada. Air quality advisories were in effect for much of Canada and had been issued for Pittsburgh, Philadelphia and New York City as the smoke descended from the upper levels of the atmosphere.
The AQI reading in New York City Tuesday afternoon was an unhealthy 122, the highest this year so far. At this elevated number, health effects can be immediately felt by sensitive groups. Healthy individuals may experience difficulty breathing and throat irritation with prolonged exposure, and should limit outdoor activity.The smoke will likely clear out overnight as a cold front moves into the area, AccuWeather notes.