See the world in vertical: Top photos by AP photojournalists

Heavy smoke from wildfires in Canada and Minnesota is spreading across the Midwest and Northeast U.S., affecting millions with dangerous air pollution. Over 100 wildfires are burning in Canada, and winds are carrying the smoke southeast. Warnings about unhealthy air extend from Minnesota through Toronto and into New York. The National Weather Service advises staying indoors to avoid smoke and extreme heat. Rangers in northeast Minnesota are evacuating thousands of campers from the Boundary Waters Canoe Area Wilderness due to fires. Severe drought and heat have fueled a busy wildfire season, with large fires burning across 15 states.