Crews for two of Michigan’s largest utilities are working to restore power to more than 300,000 homes and businesses amid hot, muggy conditions after severe storms toppled trees and limbs onto power lines. More than 320,000 Michigan customers were without power as of mid-morning Wednesday. Severe storms also toppled trees in the Chicago area, damaging homes and automobiles Tuesday night after two days of heat that set a record high of 99 degrees Tuesday at O’Hare International Airport. Severe thunderstorms were expected Wednesday across the Ohio Valley, the northern mid-Atlantic coast and parts of both North Dakota and South Dakota.