Air quality alerts have been issued for states across the Northeast.
Hazy and dangerous fumes from ongoing wildfires in Canada have engulfed the skies over much of the East Coast, prompting serious air quality alerts in over a dozen states.
Canadian officials said firefighters are scrambling to put out the blazes. So far this wildfire season, Canada has seen more than 8.7 million acres burned -- an area larger than the state of Vermont.
Photos show the stark differences of the New York City skyline due to the wildfire smoke.
The wind conditions that are bringing plumes of smoke south are expected to last for several more days, experts say, as some fires in Canada continue to burn out of control.
The smoke is primarily from several wildfires burning in Quebec that is being blown south in a narrow band by an intense storm system around Nova Scotia that has not moved in several days, according to Mark Wysocki, an air pollution meteorologist who teaches at Cornell University in Ithaca, New York.
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-ABC News' Meredith Deliso
Wildfire smoke contains fine particulate matter, known as PM2.5, which are microscopic solid or liquid droplets -- often 30 times smaller than the diameter of a human hair -- that can be inhaled and cause serious health problems, according to the EPA.
PM2.5 is considered unhealthy for "Code Orange" and sensitive groups once the Air Quality Index surpasses 100, according to AirNow, a website that publishes air quality data. Once the AQI surpasses 150, it is considered "Code Red," unhealthy for some members of the general public who may experience health effects, with sensitive groups experiencing more severe effects.
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-ABC News' Julia Jacobo
New York City Mayor Eric Adams updated residents on the current situation with the dangerous air quality due to the Canadian wildfires.
He said the city's Air Quality Index, or AQI, hit 484, the highest level on record, on Wednesday afternoon. Anything above 300 is considered hazardous, according to Zachary Iscol, the commissioner for the city's Office of Emergency Management.
"Tomorrow things may improve but an AQI over 150 is still considered dangerous," he told reporters.
Adams said all outdoor events in the city were canceled Thursday and urged private groups to do the same.
"The best thing is that [people] remain indoors," the mayor said.
He reiterated advisories to close windows and to wear a mask if anyone has to travel outside.
Schools were already planned to be closed Thursday, and no decision has been made about the rest of the week, according to the mayor.
Adams said the current forecast shows the situation should improve at the end of the week but warned that the situation can change.
"It is difficult to predict the movement of the smoke," he said.
