The frigid weather Monday led the city to issue a "Code Blue" warning across the five boroughs, a designation that dictates outreach teams from the Department of Homeless Services to scour the streets to make sure the homeless find shelter.

During a "Code Blue," the city's shelter system cannot deny anyone brought in by an outreach team. The system is also responsible to with accommodating walk-ins.

WHEN WILL IT GET WARMER?

Temperatures reached as low as 4 degrees at 9 a.m., the coldest reading in New York City since Valentine's Day 2016. The coldest wind chill Monday was -17. The record low temperature for this day in New York City is -2, set in 1985.

Wind gusts were at least 30 MPH for much of the city around 5 p.m., getting to nearly 50 MPH at LaGuardia Airport.

As the wind subsides, wind chills won't be quite as harsh overnight. Expect feel-like temperatures to be just above zero degrees.

The deep freeze is slated to ease Tuesday, with temperatures at least in the upper 20s, before it ends Wednesday. Expect temperatures in the 40s that day — although with a side of rain.

HEATING AND SAFETY

The mayor is also urging New Yorkers, who are already having difficulty with their heat and hot water, to notify 311 Friday so the city can try and rectify the situation.

Call 311 or log on to NYC.gov if you have heating complaints. According to the city, landlords are required to maintain the heat inside at 68 degrees Fahrenheit or above when the temperature is 55 degrees or below outside between 6 a.m. and 10 p.m.

• What precautions should you take to say safe during bitter cold?

Between 10 p.m. and 6 a.m., landlords are required to maintain the heat inside at least 62 degrees Fahrenheit or above, regardless of the temperature outside.

The city is reminding New Yorkers to call 311 if they see a person living out on the street, as a person can suffer frostbite in 30 minutes.