The Beech Mountain Loop Trail in Acadia National Park offers panoramic views over Long Pond to Blue Hill Bay and Blue Hill Mountain. Carey Kish photo

The air quality for Memorial Day weekend is expected to improve compared with Thursday, but beyond that, it’s impossible to forecast what Maine’s summer will be like for air quality, an environmental expert said.

Martha Webster, an air quality meteorologist with the Maine Department of Environmental Protection, said that the wind, temperature and other factors make it difficult to predict beyond the next few days. But Webster said she does anticipate good air quality in Maine for the Memorial Day weekend.

Beyond that, “there are so many variables at play,” she said.

For instance, while vehicle exhausts contribute to ozone levels and overall air pollution – and during Maine’s tourist season cars clog the roads – the prevailing winds can help maintain good air quality.

“You could have a number of 90-degree days in a row, and still have low ozone levels,” Webster said.

Last summer, wildfires in Canada and the western United States contributed to worsening air quality on some days in the U.S., even in Maine.


The U.S. Environmental Protection Agency website says that long-term, “climate-driven changes in weather conditions, including temperature and precipitation, are expected to increase ground-level ozone and particulate matter. These changes worsen existing air pollution, and exposure to these pollutants leads to or worsens health problems, including respiratory and heart diseases.”

Coastal Maine experienced elevated levels of ground-level ozone on Thursday. The Maine DEP issued an “unhealthy for sensitive groups” air quality warning for higher elevations in Acadia National Park.

Sensitive groups include children, older Mainers, and people with respiratory issues such as asthma, or other health issues, such as heart conditions. These groups can still be outside, but the DEP advised people to limit exertion and avoid “prolonged” outside activities at the higher locations in Acadia.

All of coastal Maine was in the “moderate” category on Thursday for ozone levels and particle pollution, while northern Maine and the western mountains were in the “moderate” category for particle pollution and “good” category for ozone levels.

For areas in the “moderate” category, sensitive groups should watch for symptoms such as shortness of breath, and consider limiting prolonged activities outside or high exertion.

On Friday, the entire state was expected to be in the “good” category for ozone and particle pollution.

According to the American Lung Association’s 2024 State of the Air report, six of the 10 Maine counties with reportable data received an A grade for air quality related to ozone levels. Cumberland, Hancock and York counties received C grades; Knox had a B; and Androscoggin, Aroostook, Kennebec, Oxford, Penobscot and Washington counties received A’s.

For particle pollution, of the seven counties with reportable data, five received A grades: Cumberland, Kennebec, Androscoggin, Penobscot and Hancock counties. Oxford County had a B for particle pollution, while Aroostook County got a C.

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