Toronto pedestrians walk as wildfire smoke turns the skies orange. Photo: Cole Burston/AFP via Getty ImagesThe wildfire smoke drifting into the eyes, throats and lungs of millions of Americans and Canadians this week is a stark reminder that the planet is changing in unsettling ways.The smoke, from wildfires raging in northern Minnesota and Canada, is causing dangerously bad air across the Midwest and Northeast — and could soon waft elsewhere.Air quality alerts have been issued in New York, Chicago, Toronto and more, with officials urging folks to stay inside.Zoom in: It's too early to tie these wildfires directly to climate change. But researchers have shown that human-caused climate change is making wildfires both more likely and more intense.One headline finding from a Climate Central report last year: "Per-person exposure to harmful wildfire smoke in the U.S. was four times higher during 2020-2024, on average each year, than during 2006-2019."Moreover, it's impossible for those of us in the smoke zone to avoid thinking about climate change as the skies turn to an ominous rust and our lungs begin to sting.The fires themselves have also destroyed homes and devastated local tourism. A satellite view of wildfire smoke across the Midwest and Northeast. Image: NOAA/STARThe big picture: Massive smoke events like this have happened before — most notably in 2023.They may get more common as North America's forests keep drying up, creating ideal conditions for megafires sparked by lightning and other causes.What's next: Hot and dry conditions mean the fires causing the smoke could keep burning for some time — and there's elevated risk of new fires.We may get periods of reprieve as the smoke stays high (possibly painting our skies but sparing our lungs), or gets carried elsewhere.At least one model suggests that the smoke could pour southward next week — reminding us that there's no safe port in a changing climate.The bottom line: Americans out West have long understood "fire season." The rest of us need to start thinking about "smoke season," too.