New Yorkers should prepare for hazy skies and declining air quality in the coming days as smoke from a wildfire outbreak in Ontario, Canada, drifts into the metropolitan area.

State officials issued an air quality health advisory for Tuesday for the New York City region, including the five boroughs, Rockland and Westchester counties and Long Island, due to ozone. The advisory is in effect from 11 a.m. to 11 p.m.

Young children, older adults and people with respiratory conditions, including asthma, are most at risk when air quality worsens. State health officials advised those groups to limit strenuous outdoor activity during periods of poor air quality.

The National Weather Service said smoke from the Ontario wildfires is already visible overhead and could mix closer to the surface Wednesday into Thursday, reducing visibility and potentially worsening air quality.

"If you go outside and look up right now, you'll see hazy skies, and that is smoke. It isn't quite at the surface yet, but we're expecting it to reach the surface tomorrow," said James Tomasini, a meteorologist with the National Weather Service in New York.

The air quality concern comes at the same time as brutal heat — with a heat index of up to 104 expected for the New York City area on Wednesday, and temperatures staying in the 90s through Friday.

Tomasini said forecasters are continuing to monitor the wildfire outbreak and that the smoke's impact on New York City could change as weather conditions evolve.

Canada is seeing more wildfires this season than it had at this point last year, part of what the country's federal government has described as a "worsening wildfire situation."