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

As a day progresses the air near the water’s surface can warm some and the inversion erodes. The smoke will lift and disappear into a larger space in the air over Michigan. So the strong visual of thick smoke turns into a faint haze of smoke all over the sky of Michigan.

Smoke from Canadian wildfires is engulfing much of the eastern and central United States and and is expected to continue for days.