With snow and cold wind threatening the Philadelphia region, Montgomery County, Philadelphia and other area counties declared "Code Blue" emergencies.
The alerts went into effect Monday morning and last until at least Friday in Montco and Philly.
"A Code Blue Cold Weather Declaration is made in Montgomery County when winter conditions pose a threat of serious harm or death to individuals without shelter," a Montco statement said.
"A Code Blue is called when the combination of air temperature and wind chill is anticipated to be 20 degrees or less."
Philadelphia's Code Blue alert includes getting homeless people shelter, the Philadelphia Office of Emergency Management said.
Camden, New Jersey; Burlington County, New Jersey; and Bucks County, Pennsylvania also declared Code Blues ahead of the first flake. In Bucks County, churches were being used to shelter people need to come in from the cold.
NBC10 First Alert Weather chief meteorologist Glenn "Hurricane" Schwartz issued a First Alert warning for the potential of significant snow.