A polar vortex brought very cold air across New Jersey, plunging the state into arctic temperatures.

Overnight lows were expected to be in the low single digits, not taking into account the wind chill factor.

People across the Garden State spent Wednesday getting ready for the cold.

“Two words: Thermal underwear,” says Grace Fitzgerald of Belmar. “You could walk every day in January if you wear your thermal underwear.”

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The New Jersey Office of Emergency Management issued a Code Blue for the state due to the very cold temperatures. Health experts warn residents to limit their time outside if possible. Anyone who must be outside should dress in layers and keep exposed skin covered.

“You need layers,” says Belmar resident Dave Kacska, who often walks outside in the winter. “You have to have the right undershirt and the right layers.”

State officials are also warning residents to be mindful of standing water. That water will freeze due to the frigid temperatures and could pose slippery, dangerous conditions.

Forecasters say that the cold weather is expected to stick around at least until Thursday. Conditions should warm up into the low-40s by the weekend.