The majority of US states in the Midwest and on the Northeast coast are in the grip of a brutal cold snap, threatening the most vulnerable members of society. Every night in New York city, shelters take in around 55,000 homeless people, 22,000 of whom are children. The city's new mayor, Bill de Blasio, has reinstated a Code Blue Policy after being on the job for less than a week. The law guarantees shelter to anyone whenever the temperature drops below freezing for more than four hours. Al Jazeera's Cath Turner reports from New York.
