A heavy snowfall and dangerously low temperatures has gripped the northeast of the United States.
The poor conditions have ground flights, closed schools and government offices across the region and caused at least three deaths.
Boston was hard-hit by the first major winter storm of 2014, getting nearly 45cm of snow, while some towns north of New England's largest city saw close to 60 cm of accumulation.
Major cities from Washington DC to Portland and Maine, were affected, with New York's Manhattan island getting 15cm of snow.
Snow tapered off across much of the region by midday, but dangerous cold was expected to linger into Saturday.
The National Weather Service said the mass of Arctic air would drop temperatures to 11-17C below normal, with record lows possible in some areas on Friday.
"Over the next 24 hours, we are going to see temperatures like we haven't seen in quite a while," said Peter Judge, a spokesman for the Massachusetts Emergency Management Agency.
As temperatures in New York City dropped to -10C the city's Department of Homeless Services went to "code blue," doubling the number of vans patrolling streets to seek people who needed shelter and streamlining the check-in process for homeless shelters.
The unusually cold weather extended as far south as New Orleans, where temperatures approached 2C, prompting officials to open emergency shelters for the homeless.
Some 2,076 US flights were canceled and 2,083 were delayed on Friday.
New York's LaGuardia Airport, Newark Liberty International Airport and Philadelphia International Airport reported the most cancellations.
Storm related deaths
The weather was a factor in at least three deaths.
In Kentucky, a 50-year-old woman died when she lost control of her car on an icy road near South Williamson, according to state police.
Police recovered the body of a 71-year-old woman who had wandered out in the rural western New York State town of Byron on Thursday night, improperly dressed for the single-digit temperatures, according to the Genesee County Sheriff's Office.
While in Philadelphia a city worker was killed after a machine he was using was crushed by a mound of de-icing rock salt, media said.