It's the first Code Blue of the season and officials are telling people to bundle up if you're going out, and to keep an eye out for those who may need help in this dangerous cold.
Under the twinkling lights and next to a toasty fire in Philadelphia, people gathered to enjoy the Franklin Square Holiday Festival with some layers.
Olivia Kinkel of South Philadelphia said, "Two pairs of pants, and two hoodies on!"
Nancy Matteis of South Philadelphia added, "First crisp day. We're having a good time. Hot chocolate for the kids, building ginger bread houses.
But under the Pennsylvania Convention Center on 12th Street in Center City, the scene was much different.
Because the City of Philadelphia has declared a Code Blue - anticipating dangerously low temperatures.
Outreach teams are on patrol - trying to get as many people into shelters as possible.
Marcus Gonzalez is homeless.
He said, "Cold. Very cold."
Gonzalez says he's relieved to be heading to a shelter at 25th and Lehigh. So does Danny, who says he's been homeless for about a month.
'I hear on the news a lot of people freeze to death. You know what I mean?" Danny said.
But not everyone goes willingly.
Kanika Stewart-Jones has been doing this work for about a decade. She says many people have had negative experiences in shelters, or are struggling with mental illness or addiction.
At one stop, two people did go with them to shelters.
"For all the ones that didn't come, those two make me stay out longer. Make me want to continue to do it," Kanika said.
In Camden, bundled up commuters headed home for the weekend. County officials hope people will bring their pets inside and check on their neighbors during this first cold snap.
Camden County Freeholder Bill Moen said, "We've had a very good luck with the fall weather. So going from being very lucky to very unlucky overnight could result in people being unprepared."
The city of Philadelphia has added 80 beds to homeless shelters and say there is plenty of room.
If you see someone in need of shelter this weekend in the city you can call (215) 232-1984.
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