Canadian wildfires blanket Northeast in unhealthy smoke, haze

June 7 (UPI) -- Hundreds of Canadian wildfires continued to burn Wednesday and send unhealthy levels of smoke and haze across large sections of the northeastern United States.

Air-quality warnings were issued for multiple U.S. metropolitan areas on Wednesday as the Federal Aviation Administration slowed air traffic at some major airports.

More than 400 active wildfires were burning across Canada Wednesday, with the worst affecting the eastern province of Quebec, which borders Maine, New Hampshire, Vermont, and New York.

The smoke and haze are causing unhealthy air quality levels in New York City, Boston and other northeast cities.

Rochester, N.Y., had an Air Quality Index rating of 282, making it the worst in the nation, followed by Gordonville, Pa., at 272 and Ithaca, N.Y., at 257.

Ratings between 201 and 300 are considered unhealthy.

An Air Quality Alert issued by the National Weather Service is now in effect in parts of New Jersey, New York and Connecticut through Thursday night.

The haze across the New York area caused the FAA to limit flights into and out of the Newark and LaGuardia airports because of the lack of visibility.

Tech giant Google told employees on the East Coast to work from home rather than come into the office.

"We are advising Googlers to work from home if possible, and limit their exposure to outdoor air," reads an internal memo obtained by CNBC.

The directive reportedly related to its offices in several cities, including Pittsburgh and Washington, D.C. Google issued the same message to its employees in Toronto and the tech hub of Waterloo, Ontario.

Of the 413 active fires in Canada, 249 are considered out of control, forcing 26,000 residents to leave their homes because of evacuation orders.

About 9.4 million acres (3.8 million hectares) of forest have burned so far, Canada's Minister of Emergency Preparedness Bill Blair said at a Wednesday news conference.

The country already has surpassed its annual average of approximately 6.18 million acres (2.5 million hectares) of land lost to wildfires, while the amount of scorched earth is 15 times ahead of where it stood at this point last year.

Wildfires are typically at their worst in July and August.