Canada had 857 fires actively burning on Thursday, and smoke from those fires pushed hazardous air quality into parts of Michigan, Minneapolis and Minnesota, where people were told to stay indoors. The Canadian Interagency Forest Fire Centre said 23 new fires were reported the same day.
The US Air Quality Index program described air quality in large parts of the northern states as "hazardous". Air quality alerts stretched into the Upper Midwest, the Great Lakes and the Northeast as smoke moved south from Canadian fire clusters.
Michigan and Minnesota
Detroit had the worst air quality in the world according to IQAir, while Minneapolis ranked second and Toronto third. In the affected areas, the practical instruction was the same: stay indoors while the smoke plume remains over the region.
The Canadian Wildland Fire Information System said the vast majority of the fires were burning out of control. Smoke from western areas of Ontario sent thick plumes across Thunder Bay and Toronto, while lower concentrations drifted over the Great Lakes and above New York, where hazy skies and redder sunrises and sunsets were likely Thursday.
Ontario and Quebec
Rain and thunderstorms are expected in Ontario over the next few days, but the report said they may not make much difference. Northwesterly winds are expected to keep pushing smoke into northern US states for the rest of this week and into the weekend, before a change in wind direction by Monday steers the smoke across Quebec.
That shift offers the clearest sign of when conditions may start to ease farther south in the US. Air quality there is expected to improve by Monday, but the smoke pattern keeps moving day by day until the winds change.
Upper Midwest and Northeast
The alerts now cover multiple US states, including the Upper Midwest, the Great Lakes and the Northeast. For people in Michigan, Minneapolis and Minnesota, the immediate issue is not the number of fires alone but the combination of active smoke transport and hazardous air quality already on the ground.
By Monday, the main plume should be drifting toward Quebec rather than deeper into the US, which means the worst air in the northern states should begin to ease first in the areas that were hit most directly on Thursday.
