On Saturday night the city will experience temperatures as low as 20 degrees below zero with wind chill, and we're already well on our way into the cold snap, which has prompted Mayor de Blasio to issue a Code Blue warning. When Code Blue is in effect, people who are homeless or otherwise in need of assistance can go to any shelter without having to go through the usual eligibility and intake procedures. The Department of Homeless Services also ups its efforts with response teams ready to offer transport to anyone who needs help to a shelter, drop-in center, or hospital.

De Blasio activated Code Blue yesterday evening, and it will remain in effect through Sunday.

"We'll have a very aggressive outreach effort led by our Department of Homeless Services working closely with NYPD and FDNY," he said yesterday. "As you've seen in the last few weeks, those efforts have been very effective at getting people in - overwhelmingly voluntary, some involuntary. That effort will be done with force."

During the last Code Blue warning, 30 people were taken to shelters or hospitals, 2 involuntarily.

Last night's wind chills were in the single digits, and tonight's will drop below zero, before getting as low as -23 from Saturday into Sunday. Gothamist weatherman Joe Schumacher says that "the temperature is expected to bottom out near the record low of two degrees on Sunday morning, and dropping below zero for the first time in more than two decades is not out of the question."

"These can be life-threatening conditions and people should treat that with all seriousness," the mayor said, noting that seniors, infants, people with cardiovascular or lung conditions, and people under the influence are at particular risk in the cold.

If you see someone at risk, you're encouraged to call 311, or 911 if the situation appears emergent. The mayor also reminded people to call 311 if their landlords are not providing heat or hot water, and cautioned against "improvis[ing] ways of heating their homes"—so no burning those stacks of unread Food & Wine magazines you got a free subscription for and never opened.