A significant haze from wildfires in three Canadian provinces has spread across roughly a third of the United States, forecasters reported.
Despite this extensive coverage, air quality has remained largely unaffected in many regions, with notable exceptions in New England, parts of New York state, and the Midwest.
On Tuesday, alerts were issued for various areas in Canada and the neighboring U.S. due to hazardous levels of particulate pollution linked to the smoke, particularly affecting Minnesota and stretching from the Dakotas through the Ohio Valley, the Northeast, and as far south as Georgia.
The most severe air quality issues were found in New York and New England, where the smoke was considerably thicker.
“Much of the smoke is aloft in the upper atmosphere, so in a lot of areas, there aren’t air quality issues,” said Marc Chenard from the National Weather Service on Wednesday.
However, he pointed out that areas like New York and Connecticut faced significant air quality concerns due to the smoke being present in the lower atmosphere.
Since early May, Canada has experienced numerous wildfires, with more than 212 active fires reported as of Tuesday afternoon.
The Canadian Interagency Forest Fire Centre noted that half of these fires are currently out of control, having burned approximately 2 million hectares (4.9 million acres) of land.
The majority of the fires are concentrated in the west-central provinces of Manitoba, Saskatchewan, and Alberta.
The wildfires have had devastating impacts, including the destruction of a water tanker air base in Saskatchewan and disruptions to oil production in Alberta.
Officials are warning that conditions may worsen as more communities are at risk each day.
Saskatchewan Premier Scott Moe addressed the situation in a news conference, stating, “We have some challenging days ahead of us,” and adding concerns about the potential increase in the number of evacuees.
Environmental health expert Yang Liu from Emory University emphasized that the smoke poses health risks to everyone, particularly infants, the elderly, and those in frail health.
Liu noted, “It will affect everyone at some level, all walks of life,” while describing the smoke as containing small, potentially toxic particles that can infiltrate the lungs and enter the bloodstream.
On Wednesday morning, one of the worst air quality readings in the northeastern U.S. came from Williamstown, Massachusetts, which recorded a “very unhealthy” rating of 228 according to IQAir, a global air quality monitoring service.
In contrast, an air quality index reading below 50 is considered “good,” while scores between 100 and 300 are categorized as “unhealthy” to “very unhealthy,” and any reading above that level falls into the “hazardous” category.
Other areas in the Northeastern U.S. reported much better air quality, with New York City at a rating of 56 and Washington D.C. at 55.
Meanwhile, air quality levels in parts of the Midwest have also shown improvement; Ely, Minnesota, registered a “moderate” reading of 65, dramatically lower than its previous Tuesday reading of 336.
Minneapolis, which was highlighted for having the third-worst air quality globally on Tuesday, saw its reading drop from 168 to a more manageable 96 by Wednesday morning.
image source from：https://www.aljazeera.com/news/2025/6/4/canadian-wildfire-smoke-spreads-across-a-third-of-united-states
