MINNEAPOLIS — A rapidly expanding wildfire in Minnesota's north woods spread a plume of smoke across the Upper Midwest on Tuesday, with haze smudging the sky as far away as Chicago and Milwaukee.
The haze was heavy enough that some people reported burning eyes and difficulty breathing in the Chicago area, the National Weather Service said.
The plume came from a fire in the Boundary Waters Canoe Area Wilderness, a lake-dotted region on the Minnesota-Canada border. The fire grew swiftly this week to cover nearly 160 square miles. No structures have burned, and no one has been hurt, officials said.
The residents of Isabella, a small town of about 200, were standing ready to evacuate if necessary.
The fire started Aug. 18 with a lighting strike 20 miles from Ely but began spreading quickly this week in windy, dry conditions. The fire raced 16 miles east in a single day from Monday to Tuesday.
"Nobody would have guessed it would be doubling and quadrupling in size," said Jean Bergerson, a spokeswoman for the Minnesota Interagency Fire Center.
Winds of up to 25 mph forecast for Tuesday and today were likely to spread the fire, dubbed the Pagami Creek fire for its point of origin, further. She predicted it would be days or weeks before the fire was under control.
The Wisconsin Department of Natural Resources' air quality monitor showed a spike in particle pollution throughout the day in the southeast part of the state, including Milwaukee, and it issued an air quality alert for sensitive people in the area. The smoke also reached Michigan, where forecasters said it rode northwesterly winds from a cool front.
Jim Richardson, a forecaster for the National Weather Service in Minnesota, said it wasn't unusual that the plume spread so far, noting that smoke from Arizona's massive wildfire in May reached Minnesota. Richardson said changing winds today may shift the plume more directly south of the blaze.
The Boundary Waters is a wild region popular with canoe campers for its beauty. Several lakes and entry points into the wilderness were closed, and about 120 campers were evacuated from the fire zone earlier this week, some by Forest Service float planes.