The state has issued an air quality health advisory through Thursday for all regions of New York.
Officials say contaminants from the Canadian wildfires are partly to blame.
The state says it won't get as bad as it was earlier this month, but people with underlying health conditions could be affected.
The air quality is forecasted to reach unhealthy index levels for western and central New York. On Long Island, the air quality is expected to be moderate with the biggest pollutant being ozone.
As a precaution, the MTA said free KN95 masks would be available at Long Island Rail Road, Metro-North Railroad and New York City subway stations.
Here is where you can get them.
Gov. Kathy Hochul is warning high-risk population including children, older adults and people with underlying respiratory and cardiac conditions to stay indoors as much as possible and wear a mask if they do go outdoors.
The Nassau County health commissioner encourages anyone with existing medical conditions to speak to their doctor before engaging in strenuous outdoor activity.
The Suffolk County health commissioner advises residents to seek medical attention if they experience eye, nose and throat irritation, shortness of breath or chest pain.
Doctors at Northwell Health Syosset Hospital say anyone who had a problem with the air quality earlier in the month or has respiratory issues should stay indoors to stay safe.
"We are expecting to see a few extra patients who are coming in with respiratory complaints, asthmatics, those with COPD, the elderly, the very young are more susceptible to breathing problems," says Dr. Matthew Projansky, of the Northwell Health Syosset Hospital Emergency Department.
Owner of the Coleman Country Day Camp in Merrick Ross Coleman says his summer camp will open for the first day of the season Thursday as planned, but are closely monitoring the air quality situation.
The executive director of the Usdan Summer Camp for the Arts says, "After careful consideration, Usdan will remain open tomorrow...Please be aware that due to the design of our campus, we are not able to provide indoor shelter for the entire day. Parents and guardians should make the decision that is best for their family."
Emergency cell phone alerts will be sent to New Yorkers if the air quality becomes very unhealthy in their area.
Check the air quality in your neighborhood here.
