Schools across the US East Coast cancelled outdoor activities, commercial airline traffic was slowed 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.

More than a million people were ordered Monday to evacuate the path of Hurricane Florence as the powerful Category 4 storm packing winds of 140 miles (220 kilometers) per hour bore down on the East Coast of the United States.