New York City is activating an unprecedented heat emergency plan as dangerously high temperatures are expected to grip the city through the holiday weekend.

Mayor Zohran Mamdani announced Tuesday that the city is launching several first-of-their-kind initiatives ahead of what forecasters say could be one of the most significant heat events New York has experienced in years. Heat index values are expected to climb above 90 degrees on Wednesday and could reach into the 100s by Friday.

The city will open hundreds of cooling centers across all five boroughs starting Wednesday, including libraries, public hospitals, older adult centers and other public buildings. Public schools, the Javits Center and NYC Emergency Management headquarters will also serve as cooling centers during the peak of the heat emergency.

Among the new initiatives are 15 Cooling Outreach On-Location, or “COOL,” vans staffed by nurses and paramedics. The mobile units will provide water, electrolytes, sunscreen, cooling towels and wellness checks while transporting people in need to cooling centers or hospitals. Separate in-home wellness teams will also check on vulnerable older adults.

The city is also expanding outdoor cooling stations with misting fans, cold water and cooling towels for street vendors, delivery workers and day laborers. More than 2,200 LinkNYC kiosks will begin displaying real-time walking directions to the nearest cooling center.

Officials are urging New Yorkers to stay hydrated, avoid prolonged outdoor activity during peak heat hours, use air conditioning whenever possible and check on elderly neighbors and loved ones. Anyone experiencing signs of heat-related illness, including confusion, difficulty breathing, dizziness or nausea, should call 911 immediately.

Residents can find the nearest cooling center by calling 311 or using the city’s Cool Options Map.