It’s not your imagination: The air quality in New York City took a dip this week.
The state’s Department of Environmental Conservation issued air quality advisories for the metro region on Tuesday and Wednesday. And air sensors across the city detected an increase in tiny pollution particles early this week, peaking Wednesday evening.
The city also experienced a sustained period of cold earlier this month, with temperatures beginning to rise to around average levels for this time of year only last week, according to the National Weather Service. Lows in Central Park reached nearly 25 degrees Fahrenheit below average on Feb. 8.
The fluctuation in temperature and the decline in air quality are connected, said Daniel Westervelt, a professor at Columbia University.
Usually, temperatures are cooler higher in the atmosphere, and air rising from the Earth’s surface disperses pollutants from sources like heating systems and vehicles, Dr. Westervelt said.
But the recent period of cold — and the presence of snow on the ground — created a somewhat unusual “temperature inversion,” where temperatures near the ground became cooler than those above.
“That means that there’s not a lot of vertical mixing of air,” Dr. Westervelt said. “And so that causes the pollutants to basically build up and get highly concentrated.”
Though air quality levels in New York City are usually good and have improved over time, air quality index measurements ranged from “moderate” to “unhealthy for sensitive groups” early in the week, Dr. Westervelt said. Children, older adults, pregnant people and those with medical conditions could be particularly vulnerable, he said.
“If you’re in one of those categories, you should take precautions,” he added. “Maybe don’t spend as much time outside; run your air filters in your apartment.”
Air quality levels in New York last dipped to such lows in August 2025, Dr. Westervelt said, when smoke from Canadian wildfires wafted to the city.
Index readings for particle pollution returned to more typical levels on Thursday.
Camille Baker is a Times reporter covering New York City and its surrounding areas.
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