Forecasters warn that hazy, grayish-blue skies could persist for many weeks as fires continue to burn, though most smoke will remain high in the atmosphere.

World leaders may face smoke warnings when they gather next week in Alberta as wildfires burned out of control across much of Canada and caused the country's second-worst fire season in decades.

Blanc, the tallest mountain in Western Europe, as a result of massive wildfires raging across Canada. The smoke has traveled thousands of miles, crossing the Atlantic to reach the French-Italian Alps.