A thick haze is hanging over parts of New York City today—and health officials say it’s not just fog.

An Air Quality Health Advisory is in effect through midnight Thursday for Brooklyn and the rest of the NYC metro area, as smoke from a fast-moving wildfire in New Jersey drifts into the region.

The New York State Department of Environmental Conservation (DEC) and the Department of Health (DOH)issued the alert for elevated levels of fine particulate matter, or PM 2.5. These tiny particles, which can come from wildfires and other combustion sources, can be harmful when inhaled—especially for children, seniors, people with asthma, heart or lung conditions, pregnant individuals, and outdoor workers.

Health officials are urging people in these sensitive groups to limit time outdoors, avoid strenuous activity, and watch for symptoms like coughing, throat irritation, or difficulty breathing.

The smoke is tied to a massive wildfire that broke out around 9:45 a.m. Tuesday in the Greenwood Forest Wildlife Management Area near Barnegat Township, New Jersey. The fire has already burned more than 13,200 acres and forced the evacuation of thousands of homes, while also causing power outages across Ocean County. It is still only partially contained as of Thursday morning.

Air quality levels are expected to reach Level Orange (AQI 101-150), which is considered unhealthy for sensitive groups.

A toll-free air quality hotline has been set up for New York residents: 1-800-535-1345.

For more updates, visit dec.ny.gov