Wildfire smoke has become the leading contributor to poor air quality across New England in recent years, particularly during the summer when wildfire season in Canada reaches its peak, sending smoke plumes drifting far and wide.
Each New England state has seen an uptick over the past five years in the number of days that fine particulate matter or ozone exceeds air quality standards, reaching levels considered “unhealthy for sensitive groups.”
Although wildfires across the western United States are a major problem, in New England it’s important to focus on Canada because of the jet stream during the summer, which usually rides along the US-Canadian border.
Hot smoke plumes rise high in the atmosphere and can travel thousands of miles. If a strong surface high-pressure system is nearby, the sinking air can pull smoke to the surface, which is what the region has seen this week.
This summer and the previous two have delivered major smoke episodes across most of New England. In 2023, Canada had its worst wildfire season on record, with nearly 43 million acres burned.
In 2024, Canada had its sixth-worst wildfire season on record, and the current season is a lock for the second-worst, with nearly 17 million acres already charred. Boston and much of New England has felt the impacts of such extensive wildfire seasons.
Take a look at the annual hectares burned in Canada since tracking began in 1983.
The Massachusetts Department of Environmental Protection shared the number of days when ozone and fine particulate matter exceeded the threshold to issue alerts.
In 2021 and 2022, air quality alerts were issued on six days. But in 2023, when the state issued alerts on a record 19 days, coinciding with the historic Canadian wildfire season. Fires raging over central and eastern Canada, specifically the Quebec region, were responsible for the increase in poor air quality days. With wildfires burning much closer to home, the smoke doesn’t have to rise or travel as far to reach the region.
Last year, there were only 10 days when parts of Massachusetts were under air quality alerts, and there have been eight days so far this year. Numbers are similar in the other New England states.
The clear rise in the frequency and intensity of smoke events reaching New England is mainly driven by more prolonged drought and heat intensity across Canada and the western United States, each of which stems from climate change. Heat speeds up evaporation and depletes moisture from vegetation on the ground, and drought will make vegetation more vulnerable to combustion in the event of a lightning strike or human-caused ignition.
Although New England historically has relatively clean air, the increase in the number of poor air quality days can disrupt outdoor plans and, most importantly, your health.
Air quality alerts should be taken seriously, especially by people with heart or lung disease, such as asthma, older adults, children, teenagers, and people who are active outdoors.
Ken Mahan can be reached at ken.mahan@globe.com. Follow him on Instagram @kenmahantheweatherman.