Skies have cleared across Michigan, after smoke from wildfires in Canada brought record air pollution.
That doesn't mean the fires have stopped. Dozens of fires are ongoing in British Columbia, Alberta, Western Ontario, and Quebec.
Chris Stockdale is a fire research scientist with Natural Resources Canada. He says these fires are hard to fight in conventional ways.
"When the fires ignite, the control measures are very limited, but the intensity of these fires is such that direct attack — like from humans on the ground — is impossible. It's way too hot. People can't get within hundreds of meters of these things, I mean the heat exposure would be fatal," he says.
Changing weather patterns are now pushing the smoke toward Minnesota, with the Twin Cities getting record smog.
So far, fires in Canada have burned around 20,000 square miles — roughly twice the yearly average.