Thousands of visitors have been told to evacuate a remote Minnesota wilderness area because of wildfires sending heavy smoke across the U.S. Midwest and Northeast. More than 100 wildfires are burning in Canada, with winds carrying the smoke southeast. Warnings about unhealthy air conditions extended from Minnesota through Toronto and into New York. Rangers are working to evacuate 6,000 to 10,000 campers from the Boundary Waters Canoe Area Wilderness. Severe drought and heat have created a busy wildfire season. Officials warn that large fires could burn for months, affecting air quality across several states.