It could be several more days before electricity is restored to areas hit by vicious storms that killed at least 13 people and left 3 million power customers to negotiate sweltering temperatures without air conditioning. Across a swath from Indiana to New Jersey and south to Virginia, officials warned the heat wave could take a toll on the elderly, young or sick. Problems from the storms that began last Friday ranged from a damaged prison in Illinois to tree-strewn train tracks that stranded 232 Amtrak passengers for more than 20 hours in West Virginia.