A blanket of Canadian wildfire smoke, thick enough to block out the sun and hazardous enough to spur warnings for Long Islanders to stay inside, remains stubbornly in place until late Thursday at the earliest.The state issued a late-morning warning Thursday that Long Island and the NYC metro will be breathy air considered "unhealthy" for the rest of the day.The National Weather Service predicted "patchy smoke," high humidity and heat hitting 90 degrees Thursday. The temperature should drop to about 72 on Thursday night under smoky skies.It will all be close to a repeat of Wednesday, when forecasters said the smoke from wildfires in Ontario, Canada, first settled in above Long Island, thickened by shifting winds and carrying a light scent of burning wood.WHAT NEWSDAY FOUNDA blanket of Canadian wildfire smoke is forecast to remain stubbornly in place until late Thursday at the earliest.The smoke, which settled above Long Island on Wednesday, comes from smoke blown southeast from wildfires in Ontario, Canada.Long Islanders are urged to remain indoors Thursday, avoid strenuous outdoor activities and, if possible, wear an N95 mask or other face covering."We're in a very serious health situation right now in the State of New York," Gov. Kathy Hochul said Thursday. "The smoke from the Canadian wildfires that covered the state [Wednesday] are going to continue blanketing the state all day today. This is bad news for every New Yorker. There'll be great impacts."Just how bad it could get breathing the outside air remained an unanswered question, said weather service meteorologist David Stark on Wednesday.Forecasters said it's unclear how long the smoky conditions would last. The next chance of smokeless skies is Friday, when the high tops out at about 87 with a mix of clouds and sun, according to the weather service's online forecast map. The forecast also calls for winds between 5 mph and 8 mph. The Robert Moses Causeway bridges over the Great South Bay in Babylon on Wednesday, with the wildfire smoke blocking out the blue sky. Credit: Newsday/Steve PfostAn air quality warning will remain in effect through 11:59 p, m, Thursday, with unhealthy conditions for all groups, according to the U.S. Air Quality Index. During the 2023 wildfires in Quebec, Hochul said, asthma-related emergency department visits increased by 82%. The state is expecting a spike this week as well."And so I'm going to say this over and over and over, between now and tomorrow, if there's any way you can possibly stay indoors, please do not venture out." Hochul said. "Shorter dog walking. Please keep the babies inside. Senior citizens, just hold on and stay home for another day and a half."Hochul also encouraged employers with employees who normally work outside to let them stay indoors today and tomorrow. The state is also urging summer camps to consider suspending outdoor activities.New Yorkers who have to go out should consider wearing a mask, she said.The state is making N95 masks available to any county that requests it. And in New York City the MTA and Port Authority has masks available to commuters at Penn Station, Grand Central, Times Square, Jamaica, and the Port Authority bus terminal.The New York State Department of Environmental Conservation issued the air quality health advisory for Long Island and other parts of the state for Thursday. The advisory warned of fine particulate matter, also known as PM2.5. "These particles come in many sizes and shapes and can be made up of hundreds of different chemicals." the U.S. Environmental Protection Agency says on its website. "Some are emitted directly from a source, such as construction sites, unpaved roads, fields, smokestacks or fires. ... Some particles less than 10 micrometers in diameter can get deep into your lungs and some may even get into your bloodstream."State Health Commissioner Dr. James V. McDonald cautioned that older residents and those predisposed to respiratory problems should remain indoors to avoid the effect of the airborne particulates generated by the wildfires. For anyone going outdoors Thursday, he recommended using an N95 mask. It would also be a good idea to finish any outdoor work earlier in the day, McDonald added.K. Max Zhang, a sustainable energy systems expert at Cornell University who studies the effects of pollutants on air quality, said this year's smoke will not be as bad as the June 2023 wildfires that choked New York."The wildfire smoke now affecting New York is the latest example of what is becoming a new summer reality for the state," Zhang said in an email. "The pattern is increasingly clear: episodic wildfire-smoke pollution is no longer rare."Newsday's Carl MacGowan contributed to this story.