A powerful snowstorm is sweeping through the north-east US, with warnings in place for 14 states affecting more than 60 million people.
Some parts of Pennsylvania and New York are predicted to see as much as two feet (60cm) of snow.
The National Weather Service (NWS) has warned of “dangerous, if not impossible travel conditions and isolated power surges” in the worst affected areas.
Two people died in a crash involving dozens of cars in central Pennsylvania.
Officials say they do not expect the storm to disrupt Covid-19 vaccine distribution, which began in the US on Monday. However, there were reports of some coronavirus testing centres in several states being temporarily closed.
Forecasters said the storm could dump up to two feet of snow in an area stretching from eastern Pennsylvania to New York’s Catskill Mountains, with a foot or more in the rest of the north-east.
Some areas will see more snow “in one event than they have seen all of last winter”, the NWS warned.
Parts of Centre County in Pennsylvania were hit with up to 33cm of snow by Wednesday night, according to the NWS.
Police in Pennsylvania said a pile-up left two people dead on the Interstate 80 in Clinton County. Multiple people were also injured in the crash which involved between 30-60 vehicles.
Six people were also hurt in a separate multi-car collision in New York City, involving 27 vehicles.
In New York, Mayor Bill de Blasio warned that the storm could be the biggest the city has seen in several years, warning residents to “take this seriously”.
Schools across the city have moved to online learning, outdoor dining has been suspended and ferry routes in the city have stopped.
Hundreds of flights have been cancelled and rail services suspended across the north-east.
US Secretary for Transportation Elaine Chao warned those in the path of the storm “to know that’s expected for your area and don’t drive in dangerous conditions”.
Coronavirus testing sites in a number of states including New York, Pennsylvania, Connecticut and Maryland have closed, CBS News reports.
Officials say they are monitoring any potential impact of the storm on the delivery of the Pfizer/BioNTech vaccine to hospitals.
“We’re following all of that,” Health Secretary Alex Azar said. “We have prepositioned Centres for Disease Control and Prevention people at each place receiving people. This is FedEx, this is UPS express shipping – they know how to deal with snow and bad weather, but we are on it and following it.”
New Jersey Governor Phil Murphy warned residents to wear a mask if they helped their neighbours shovel snow.
Bob Oravec, a Weather Service meteorologist told the New York Times: “The snowstorm is going to have a huge impact on travel. It will be an issue, but it is not going to be an event that is too long lasting.”