A big winter storm struck most of the U.S. Northeast on Thursday, leading to cancellations or delays of thousands of flights nationwide. Heavy snow, whipping wind and freezing cold swept the Northeast as blizzard warnings were issued for parts of Long Island of New York State and coastal New England, and winter storm warnings were in effect for parts of the Lower Great Lakes region, the U.S. National Weather Service said Thursday. About one-third of the country with about 100 million people in 22 states was in the path of this winter storm, the most severe one this winter so far. As of Thursday night, parts of upstate New York and northern Boston in the state of Massachusetts had snow of more than 18 inches (46 cm) deep. Snow also covered Washington D.C., the capital city, where the snowfall started late Thursday afternoon. This storm is expected to raise havoc this week by dumping heavy snow and spreading subzero wind chills across parts of the region, said the weather service. A total of 2,542 flights were canceled and 10,239 flights delayed on Thursday as a result of the winter storm, according to Flightaware.com, a website that monitors flights. New York Governor Andrew Cuomo declared a state of emergency for the whole state on Thursday afternoon, shutting down parts of Interstate highway-84, and closing Interstate-87 since midnight. The Long Island Expressway were also closed at the border between Nassau County and the Queens borough of New York, reports said. Many schools in New England and New York were already closed ahead of the snow storm, and such school closures will be widespread on Friday to ensure safety of the students. Boston Mayor Thomas Menino urged local residents on Thursday to take precautions, including taking public transportation and taking care of one another in face of the winter storm