Wildfire smoke is dense enough in a handful of states that experts recommend masks for those who can’t stay indoors.

Wildfires in Canada are pouring thick clouds of smoke into the US and will usher in unhealthy air quality for millions of people in Northeast and Midwest.

Wildfires in Canada are pouring thick clouds of smoke into the US and will usher in unhealthy air quality for millions of people in Northeast and Midwest.