Hot dogs, beach days and iced tea on the porch are some of the rites of summer. But in an era of global warming, a new ritual has emerged: quelling the smoke from wildfires burning hundreds of miles or more away.

The Midwest, Northeast and parts of Canada have been bombarded by thick smoke that has turned the skies an eerie shade of orange and prompted widespread air quality alerts. The source? Fires burning in Minnesota and western Ontario.

Canada is where the most fires are burning, with 119 fires out of control across the country as of Friday afternoon. The fires burn so intensely that smoke rises into the atmosphere and is carried by the jet stream to the east. That’s how Chicago and Detroit ended Friday with the worst air quality in the world. New York and Washington, DC also made the top 10 list.

Unhealthy air has cities telling residents to stay home and residents looking for ways to reduce their exposure to harmful wildfire smoke. While fresh air is expected to arrive at least in some places this weekend, the fires show no signs of slowing down and could mean more smoke later this summer.

The burning of fossil fuels has increased the likelihood of destructive wildfires and, with them, more frequent smoke events. The days of orange skies hitting the East Coast this week date back to 2023, when Canada’s worst wildfire season on record sent plumes of smoke across the region. Similar scenes have played out in Europe this summer as fires rage through Spain, and we’ve seen orange skies as far away as Australia and California at various times in recent years.

Research published last year shows that things are likely to get worse unless the world reduces its use of coal, oil and gas. The Nature study found that smoke from wildfires is projected to cause an excess of 71,420 deaths annually by mid-century in the US alone, a 73 percent increase compared to the 2010s. Between now and then, researchers estimate, up to 1.9 million people in the US will die from smoke-related health problems.

Below is what this week’s smoke invasion looks like. It is almost certainly a precursor to worse outbreaks if temperatures continue to rise.

Toronto, Ontario