Air quality alerts can change quickly during wildfire smoke events. Here’s what Code Orange, Code Red, Code Purple and Code Maroon mean, and when you should limit time outside.

More than 100 million people are under Air Quality Alerts, many of which note that the air pollution is so high, even healthy adults will be affected.

A dramatic video on Wednesday showed a freight train in Ontario, Canada surrounded by wildfire flames, as workers requested an emergency rescue.