Canadian wildfires burning across northern Manitoba and Saskatchewan are sending smoke through central Canada, the Great Lakes region and the northeastern United States, reducing air quality and visibility in major cities.
Here are the key things to know:
Air quality alerts were issued across the Upper Great Lakes and the northeastern United States on Monday.
The air is expected to improve for most areas by Wednesday.
The worst smoke concentrations are in the smallest towns in Canada, nearest the wildfires, and are creating hazardous air quality that could be harmful to people breathing the air.
Farther away from the fires, a strong haze is sinking to the surface this morning, creating unhealthy air quality from Milwaukee to Buffalo, including other major cities like Detroit and Toronto.
This poor air has prompted air quality alerts across the Upper Great Lakes and in the northeastern United States on Monday, forecasters with the Weather Prediction Center said.
An air quality reading that is above 150 in many of these cities is considered unhealthy, and can create ill effects that might start to be felt even by people who are not in sensitive groups.
Cities along the East Coast, including New York City, were also experiencing hazy skies on Monday. But as of early afternoon, the air quality sensors in the area were registering less than 100, so the air pollution at that location is considered below the level that is known to cause adverse health effects.
“Concentrations will increase into Monday afternoon,” forecasters in the National Weather Service office in New York City said Monday morning.
If the air quality reading climbs above 100 on Monday afternoon, outdoor air may be safe for many people, but older adults and children would be at risk, as would people of any age with heart or lung disease.
Beyond Monday, the smoke may lift back to the north and out of New York, and may linger across the Great Lakes and Midwest through Tuesday, but concentrations are expected to begin dispersing, improving air quality across the region by Wednesday.
With wildfires still active, and as weather patterns change, the smoke may once again blanket the same region over the next several weeks, as it has several times already this summer.
There is also a smoky haze in California — not from the Canadian wildfires but from local fires, like the Gifford fire, which has burned more than 60,000 acres since Friday.