Much of the New York City region was under an air quality advisory on Thursday as smoke from one of New Jersey’s largest wildfires in two decades made its way north.

The fire, which has been burning in Ocean County since Tuesday morning, has grown to 15,000 acres, mostly in the heavily forested Pine Barrens. Earlier this week, the fire forced officials to shut down the Garden State Parkway for miles and prompted the temporary evacuation of thousands of people in Ocean and Lacey Townships, the state’s Forest Fire Service said. A man has been charged with arson.

Smoke from the fires spread over a large portion of New Jersey on Tuesday and Wednesday, prompting warnings about the air quality and at times irritating peoples’ eyes and making it difficult to breathe. By early Thursday, the smoke had spread to the north, prompting an air quality health advisory that was in effect through the end of the day for New York City as well as Nassau, Suffolk, Westchester and Rockland Counties. The New York State Department of Environmental Conservation warned that the air quality index, a measure of pollutants, was likely to climb above 100, which means the air is unhealthy for sensitive groups like very young people or those with asthma or other respiratory problems.

At 5 a.m., the air quality index for the New York City region had reached 83, while Newark was at 80 and Philadelphia at 77, all within the moderate risk category. Nearby, Long Island was at 33, which is categorized as “good.”

By early afternoon, the index as at 67 in New York, 72 in Newark and 76 in Philadelphia, while Long Island had inched up to 40. The air quality advisories were in effect through midnight.

Southwesterly winds on Thursday afternoon were expected to spread the wildfire smoke toward Long Island.

“New York and Long Island, especially Long Island and the boroughs in New York are most at risk today,” said Brian Hurley, a meteorologist with the Weather Prediction Center. “Also southern parts of upstate New York, south of Albany and southern Poughkeepsie, but it’s really confined to the metro region.”

By Friday the smoke is expected to thin and clear, as stronger winds develop and rain spreads to the region later in the day. There have been no injuries and no homes were damaged as the fire has spread west through the mostly forested area of the Pine Barrens, part of a containment strategy meant to protect homes closer to the coast. On Wednesday, the authorities said they expected the fire to grow even as efforts to contain it gained ground.

Fire authorities said the blaze may become one of the largest wildfires in the state since 2007, when a flare dropped by an F-16 fighter jet ignited a fire that ultimately consumed 17,000 acres.

Much of the state was at elevated risk for wildfires this week, and by Wednesday the entire state was under a “high” rating, the middle point of a five-point scale that the state uses. Fuel like dry grass that would help any fire spread more easily has been especially dry, as the southern part of the state remains in drought conditions. Rain toward the end of the week is expected to give firefighters a helping hand in bringing the fire more under control.

“There’s going to be slight chance of rain later Friday and into Saturday,” Mr. Hurley said. “Saturday is going to be the day with the best chance of rain. So that will definitely help.”