Reuters: The United States experienced its coldest winter in nine years in December as snow storms swept across the country, private weather forecaster Planalytics said on Monday. Every region in the United States trended colder than normal, Planalytics said, which helped boost energy prices as consumers nationwide turned up their heating. “Following the warmest November since 2001, the month of December 2009 ended the coldest since 2000,” Planalytics said on Monday. The highly …