Intense Canadian wildfires are blanketing the northeastern US in a haze, turning the air acrid and the sky yellowish gray.Schools across the US East Coast cancelled outdoor activities, flights were halted and millions of Americans were urged to stay indoors on Wednesday as smoke from Canadian wildfires drifted south, blanketing cities in a thick yellowish haze.
The reduced visibility caused by the haze forced the Federal Aviation Administration to slow or halt some flights into New York City at LaGuardia International Airport and Newark Liberty International Airport. In some areas, the Air Quality Index , which measures major pollutants including particulate matter produced by fires, was well above 400, according to Airnow, which sets 100 as "unhealthy" and 300 as "hazardous."