The blaze has swallowed at least 160 square miles at the Boundary Waters Canoe Area Wilderness, making it one of the largest on record in the state, U.S. Forest Service spokeswoman Lisa Radosevich-Craig said. Smoke from the fire drifted as far as Chicago and Milwaukee on Tuesday.
Radosevich-Craig said about 200 highly experienced firefighters from federal and state agencies will join the battle against the wildfire that was ignited by a lightning strike on Aug. 18. The flames spread quickly because of high winds and dry conditions, but she said firefighters are hopeful that less powerful winds mean the fire will not grow by more than a quarter of a mile on Wednesday.
No buildings have burned and no injuries have been reported, even after the fire raced 16 miles in a single day from Monday to Tuesday. The some 200 residents of Isabella, a nearby town, were standing ready to evacuate their homes if needed.
"Nobody would have guessed it would be doubling and quadrupling in size," said Jean Bergerson, a spokeswoman for the Minnesota Interagency Fire Center.
The Boundary Waters wilderness is popular with canoe campers. Several lakes and entry points into the wilderness have been closed, and about 120 campers were evacuated from the fire zone earlier this week, some by Forest Service float planes.
Sections of the Boundary Waters Canoe Area Wilderness remain open, but Bergerson recommended that campers call ahead as many entry points and lakes have been closed due to the fire.
The haze was heavy enough that some people reported burning eyes and difficulty breathing in the Chicago area, about 600 miles south of the forest fire, the National Weather Service said.
The Wisconsin Department of Natural Resources agency's air quality monitor showed a spike in particle pollution throughout Tuesday in the southeast part of the state including Milwaukee, and it issued an air quality alert for sensitive groups in the area.
The haze forced Miller Park officials to close the stadium's roof before the Milwaukee Brewers took the field for a game against the Colorado Rockies, park officials said. The smoke also reached Michigan, where forecasters said it rode northwesterly winds from a cool front.
A strong cold front moving through the area should limit the amount of smoky haze drifting into other states Wednesday, said National Weather Service meteorologist Rick Hiltbrand in Minnesota.
Twenty mph wind from the northwest should push the smoke plume southeast, but the front will cause it to ventilate before reaching other states as it did on Tuesday, Hiltbrand said. A high of just 45 was expected in the Boundary Waters area Wednesday, according to forecasters.
While the latest fire has grown quickly, it has done less damage than the 2007 Ham Lake fire, which destroyed nearly 150 buildings worth more than $10 million as it raced across 118 square miles in Minnesota and Canada. A fire in Red Lake in 1931 consumed about 1,550 square miles and killed four people.