Maine’s air quality index was downgraded Wednesday as smoke from Canadian wildfires continues to drift over the state. Conditions are forecasted to remain the same on Thursday.

Martha Webster, air quality meteorologist with the Maine Department of Environmental Protection, said that because of prevailing winds and other factors, air quality is difficult to forecast.

The remains of a home smolder in Jasper, Alta., on July 26. Wildfires encroaching into the townsite of Jasper forced an evacuation of the national park. Amber Bracken/The Canadian Press via AP

“What I can say with confidence is that with all the wildfires out there, there’s a lot of smoke aloft,” Webster said. “When and where and how much will be brought down to the surface is hard to say.”

But Webster said Canadian fires – both in western Canada and northern Quebec – caused the smoke, and they expect to be monitoring it closely for the next few weeks.

The Maine DEP is reporting particle pollution as “moderate” for the most heavily populated southern and coastal regions of the state. At the “moderate” level, “sensitive people should consider reducing prolonged or heavy exertion. Watch for symptoms such as coughing or shortness of breath,” according to the DEP.

Air quality in the northern regions of the state is classified as “unhealthy for sensitive groups.” That means “people with heart or lung disease, the elderly, teenagers and children should reduce prolonged or heavy exertion. It is OK to be active outside, but take more breaks and do less intense activities.”

Canadian wildfire smoke is causing hazy skies throughout New England, although air quality so far has not been declared a significant risk factor.

Last summer, smoke from Canadian wildfires caused dense haze and public health warnings across the Northeast. Maine avoided the high levels of smoke pollution experienced in much of the region because prevailing winds prevented worse conditions.

Climate change is contributing to more wildfires in dry regions of Canada and the U.S., making poor air quality from wildfire smoke more likely to be a recurring event, experts say.

Gail Carlson, assistant professor of environmental studies at Colby College, said the simple explanation for why climate change is causing more wildfires is because “we have hotter and hotter temperatures, and in many parts of North America we have much drier conditions, and so then the land becomes a tinder box.”

Carlson said the health impacts of wildfire smoke are continuing to be studied, including how the smoke could affect pregnancies and neurological conditions, in addition to the more obvious risks to cardiovascular health.

“We are trying to understand and characterize what the risks are,” Carlson said. “Wildfire smoke is a complex mixture of different pollutants, including carcinogenic gases.”

The forecast for Thursday is the same as for Wednesday, according to the DEP. “However, we will be keeping a close eye on the situation,” according to the agency’s forecast.