As temperatures continue to plunge up and down the northeast corridor, Mayor Bill de Blasio has declared a Code Blue in New York.

The emergency designation has particular importance for the city's homeless. 

"The City is using every resource at its disposal to reach vulnerable individuals," de Blasio said in a statement. The mayor also encouraged "New Yorkers to do their part and call 911 or 311 if they see people in need of assistance."

RELATED: De Blasio doubles number of homeless drop-in centers

When Code Blue warnings are in effect, anyone in New York in need of assistance has access to emergency shelters. The city also ramps up its homeless outreach efforts. Last night, for instance, municipal workers helped 30 people move from New York streets into emergency shelters.

So far this year, city officials say they have made over 240 placements into shelters or hospitals during Code Blue periods.

RELATED: Philadelphia declares Code Blue as temperatures dangerously plunge

Homeless drop-in centers are open 24-hours during Code Blue declarations, too, and the city offers what it calls "low-threshold housing options" which allow chronically homeless New Yorkers to go directly from the street to a warm bed.

The city added that New Yorkers can sign up for NotifyNYC alerts online or call 311 for more information.