Millions of Americans in seven states are being advised to remain indoors as thick wildfire smoke from Canada descends across the Northeast and Midwest, causing air quality to reach dangerous levels. Air quality alerts are in effect for Connecticut, Illinois, Indiana, Michigan, New Jersey, New York, and Wisconsin.
The smoke contains fine particulate matter, known as PM2.5, which can penetrate deep into human tissue and cause respiratory problems. Some areas are forecast to experience air quality ranging from "Unhealthy for Sensitive Groups" to "Very Unhealthy," with potential brief spikes into the "Hazardous" category, the Environmental Protection Agency's highest designation.
Most alerts are scheduled to last until Wednesday evening, though Michigan and Wisconsin may experience hazardous smoke conditions through Thursday. Health officials are advising residents to limit outdoor activities, avoid strenuous exercise, and keep windows closed. Individuals with pre-existing respiratory or heart conditions, as well as older adults and young children, are considered most vulnerable.
Across Canada, more than 800 wildfires are actively burning, particularly in the Northwest Territories, Saskatchewan, Manitoba, Ontario, and Quebec. This has led to significant smoke plumes drifting south into the United States.
Meteorologists predict that smoke conditions could worsen through Thursday in parts of southern New England, most of New York State including the New York City area, and extend into Pennsylvania and New Jersey. Lower Michigan and northern Ohio are also expected to experience heavy smoke.
AccuWeather forecasts "Dangerous" air quality in Rochester and Buffalo, New York, "Very Unhealthy" conditions in Boston on Wednesday, and "Unhealthy" air in New York City and Detroit. New York City Mayor Eric Adams has urged residents to avoid unnecessary outdoor activities and seek indoor spaces with air conditioning, especially noting the increased sensitivity among vulnerable populations.
PM2.5 particles are particularly harmful due to their microscopic size, allowing them to bypass the body's natural defenses and lodge in the lungs. Exposure can lead to coughing, shortness of breath, chest tightness, and eye and throat irritation, with prolonged exposure linked to more severe cardiovascular and respiratory issues.
Michigan's Department of Environment, Great Lakes and Energy issued a statewide alert warning that fine particulate pollution could reach "Unhealthy" levels, with hourly concentrations potentially spiking into the "Very Unhealthy" and "Hazardous" ranges, especially in the northern parts of the state. Residents are encouraged to use central air conditioning with high-efficiency filters, such as MERV-13 or higher, and keep windows closed.
The Wisconsin Department of Natural Resources indicated that 24-hour air quality could reach "Very Unhealthy" levels, with short-term conditions possibly hitting the "Hazardous" category. The advisory is expected to continue through Thursday, with potential extensions based on smoke conditions.
New York State's Department of Health is recommending limited strenuous outdoor physical activity, particularly for children, older adults, and individuals with existing health conditions. Connecticut and Illinois are also experiencing elevated fine particle pollution, with officials in both states urging residents to reduce prolonged outdoor activity.
New Jersey has declared a Code Orange Air Quality Action Day, classified as "Unhealthy for Sensitive Groups." The state's Department of Environmental Protection advised residents to avoid strenuous outdoor exercise until air quality improves.