Officials in New York City have issued an air quality alert, advising more than 10 million residents to stay indoors if possible.

Ground-level ozone is causing the alert. It is created when air pollution mixes with high temperatures. The temperature is forecasted to exceed 80°F on Wednesday.

Ground-level ozone is a harmful pollutant that can irritate the lungs, causing coughing, throat irritation, and chest pain.

Officials warned that people with respiratory issues, young children, and the elderly should limit outdoor activities.

An Air Quality Health Advisory is in effect from 11 am to 11 pm ET for New York City, the Bronx, Kings, Queens, Rockland, and Westchester counties, as well as the Lower Hudson Valley, which includes Dutchess, Orange, Putnam, Sullivan, and Ulster counties.

‘When outdoor levels of ozone are elevated, going indoors will usually reduce exposure,’ the alert reads.

‘Individuals experiencing symptoms such as shortness of breath, chest pain, or coughing should consider consulting their personal physician.’

The alert comes as the Midwest is also facing air quality emergencies due to wildfire smoke crossing the border from Canada. 

An Air Quality Health Advisory is in effect from 11 am to 11 pm ET for New York City, the Bronx, Kings, Queens, Rockland, and Westchester counties, as well as the Lower Hudson Valley (stock)

Smoke forecast Canada and the US. Wildfire smoke wafts across the US as horrifying map reveals where hazed air quality may turn deadly

The National Weather Service reported Air Quality Index (AQI) levels will exceed 100 today, a range classified as ‘unhealthy for sensitive groups.’

The AQI measures the amount of pollutants and particulates in the air on a scale of zero (good) to 500 (hazardous). 

The New York State Department of Environmental Conservation (DEC) issued the warning this week, explaining that ground-level ozone forms when sunlight hits pollution from cars, trucks, and industrial facilities.

This isn’t the ‘good ozone’ high up in the atmosphere that protects us from the sun’s rays, this is a harmful gas that hangs close to the ground, contributing to hazy skies and breathing problems.

‘People think of air pollution as smoke or smog you can see,’ the DEC said. 

‘But ozone is different, it’s a clear gas that you can’t see, but you can definitely feel it when you’re outside on a hot, muggy day.’

Ozone pollution is most dangerous in the afternoon and early evening when the sun is strongest. 

In the New York metro area, including Brooklyn, Queens, Manhattan, and the Bronx, millions are at risk during these high ozone days, when ground-level ozone reaches unhealthy levels that can harm people’s health and the environment. 

The alert comes as the Midwest is also facing air quality emergencies due to wildfire smoke crossing the border from Canada. Smoke rises from Edith Lake wildfire, which forced the evacuation of the nearby town of Swan Hills, Alberta, Canada in an aerial photograph

Officials are urging residents to take simple steps to cut back on pollution and save energy. 

These include using public transit, combining car trips, setting the air conditioner to 78 degrees, and limiting appliance use to after 7 pm The DEC also recommends turning off unused lights and avoiding outdoor burning.

‘It doesn’t take a science degree to help clear the air,’ the agency said. ‘Drive less, cool smart, and give your lungs and your neighbors a break.’

New Yorkers can check daily air quality updates through the state’s online resources and are encouraged to make small changes that add up to cleaner air and safer summers for everyone.

Officials warned that alerts like this should be expected as the summer begins.

The health alert in New York comes as Canadian wildfire smoke is blowing over into the US, triggering air quality emergencies in several states.

As of Wednesday, parts of Minnesota, Iowa and Wisconsin are facing unhealthy air.

More than 200 fires are burning in Canada, with over 100 considered out of control. 

While officials urge Americans to stay prepared, they note the current situation is less hazardous than in 2023, when Canadian wildfires turned skies across the Northeast a hazy orange.

Huge swaths of the US , from the north east to the Great Lakes, were blanked in smog for several days as a result.

New York City Mayor Eric Adams urged millions of residents to remain indoors as a sheet of smoke from the wildfires left hose in Manhattan unable to see the New Jersey skyline across the Hudson River.

Similar air quality alerts were also issued in Massachusetts, New Hampshire, Pennsylvania, Maryland, Illinois, Virginia and the Carolinas.