As the climate changes, the far north is drying and warming, which means wildfires are getting bigger and more intense. The area burned in Canada is now the second largest on record for this time of year,

Wildfires in Canada have forced thousands of residents to evacuate in three provinces, impacting air quality in the U.S. — and smoke from the deadly fires has even blown across the Atlantic and reached parts of Europe.

In the upper Midwest of the United States, Michigan, Wisconsin and Minnesota have issued air quality warnings as smoke from the Prairie wildfires is dragged south by a cold front. Those warnings expanded into the Northeast, causing some hazy skies.

As hundreds of wildfires burn across Canada, smoke is traveling south and potentially affecting Americans’ health. Here's why it can be so dangerous.