A powerful snowstorm is sweeping through the north-eastern 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.
New York Mayor Bill de Blasio warned that the storm could be the biggest the city has seen in years, warning residents to "take this seriously".
Schools across the city have moved to online learning, outdoor dining has been suspended and ferry routes have stopped.
According to the FlightAware website, more than 1,500 flights have already been cancelled. Some rail services have also been suspended across the north-east.
