Smoke from Canadian wildfires blanketed Hampshire County on Wednesday, bringing unhealthy air quality, orange skies and cancellations of outdoor activities.

“What you see outside are pollutants that are coming from a number of forest fires, including some more than 1,500 miles away in Saskatchewan, Canada,” said Richard Peltier, a professor in the University of Massachusetts Amherst Department of Environmental Health Sciences. “The smoke plumes ascend into the air, and then are transported by the wind.”

More than 100 wildfires are burning in Canada, with winds carrying heavy smoke southeast across the Midwest and Northeast this week. Warnings about unhealthy air conditions Wednesday extended from Minnesota through Toronto and into New York. Unusually hot summer temperatures were expected, too.

Closer to home, the Massachusetts Department of Environmental Protection issued an air quality alert on Wednesday stating that the air quality throughout the state is unhealthy for sensitive groups. The warning remains in effect until Thursday at midnight.

High levels of fine particulate matter in the air from wildfire smoke may be unhealthy for sensitive groups, such as children and people with heart or lung conditions. The particulates can cause shortness of breath, coughing, dizziness or fatigue and aggravate heart and lung diseases and other chronic health issues.

The city of Northampton also released a statement advising residents to limit outdoor exposure as the Air Quality Index in Northampton reached an unhealthy range for all individuals. The index is a tool used to report the level of air pollution and the potential health effects associated with current conditions.

“Residents are encouraged to stay hydrated, seek air-conditioned spaces whenever possible, and avoid unnecessary time outdoors,” the Department of Health and Human Services said in a statement.

The visible haze was expected to remain through Wednesday and there is a possibility for another batch of smoke to blow in on Thursday, according to Andrea LaRocca, a meteorologist with the National Weather Service.

The DEP air quality forecast for Thursday shows moderate levels, though LaRocca noted a reissuance of warnings is possible.

Dave Hayes, a severe weather spotter for the National Weather Service, posted about air quality concerns on Wednesday morning on his site called Western Mass Weather.

“With reports of smelling wood and plastic burning and AQIs in the 75-200 range this morning, it’s not amazing outside,” he wrote.

Hayes also said that Thursday may be the peak day for visible smoke, but that by Friday it should pass into the south.

According to Peltier, exposure to wildfire smoke pollutants can have long-term health effects that may show up later in life.

He noted the importance of staying inside during times like this, using a high-efficiency particulate air filter and wearing an N95 mask if spending time outside.

“Seek refuge in public buildings where clean air can be found,” he said. “Places like some houses of worship, town halls, or community spaces would be good places to start.”

Billy Spitzer, executive director of the Hitchcock Center for the Environment in Amherst, also advocated for the importance of staying inside with clean indoor air quality.

“If you don’t have or don’t want to go out and buy an air cleaner, you can make your own do-it-yourself air cleaner,” he said.

According to Climate Central’s Wildfire Toolkit, exposure to harmful wildfire smoke in the U.S. was four times higher during 2020-2024 than between 2006-2019.

This is a direct result of human-caused climate change as it “has fueled more fire activity in the western U.S., increased the frequency and intensity of fire weather, and expanded burned areas across the U.S,” according to experts at Climate Central, a nonprofit organization that includes scientists and journalists who research and report on climate change and its impacts.

“Twenty years ago, conditions like this were unusual and rare. But when we generalize about climate impacts, they are often dismissed in vague terms like temperatures that might be warmer or more or less rainfall in a given location,” Peltier said. “These smoky conditions we face today are a direct result of climate change, it’s something we can see and smell and feel and people will suffer from it. And this new normal should not be, but here we are.”

It’s been a particularly busy and deadly fire season in the U.S. About four dozen large fires are currently burning across 15 states, from Minnesota and North Carolina to Colorado, Utah, Idaho, Oregon and California, according to the National Interagency Fire Center.

Prolonged drought and record low snowpack levels combined to make conditions ripe for rapid fire growth. More than 16,800 people are assigned to fighting blazes across the country. The fires have burned over 5,678 square miles — more than the size of Yellowstone and Grand Canyon national parks combined, the agency said.

Material from the Associated Press was used in this report.