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.
Air quality is measured by the Environmental Protection Agency’s air quality index (AQI), which ranges from 0 to 500. A higher level indicates a greater level of pollution and health concern.
Levels under 100 are generally considered safe.
Totals were over 400 in New York City on Wednesday.
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The White House has postponed the Pride celebration set to take place on the South Lawn on Thursday due to the unhealthy air quality.
The largest-ever White House Pride celebration will now take place on Saturday afternoon.
-ABC News' Justin Gomez
Thursday's MLB game in Washington, D.C., between the Nationals and the Arizona Diamondbacks has been postponed due to the air quality.
The makeup game will be held on June 22.
The National Zoo in Washington, D.C., is closed on Thursday as dangerous smoke moves through the capital.
"Today's air quality is extremely unhealthy," the Department of Energy & Environment warned. "Everyone should stay indoors as much as possible, especially sensitive groups such as children, elderly, pregnant women and people with heart or lung conditions like asthma and bronchitis."
