A Special Air Quality Statement remains in effect for Prescott.
Environment Canada says high levels of air pollution from forest fires in Quebec and northeastern Ontario continue to deteriorate air quality. It says the air may improve on Thursday, before worsening on Friday.
The agency says people with lung disease, such as asthma, or heart disease, plus older adults, children, pregnant people, and people who work outdoors are at risk of health effects caused by wildfire smoke.
It recommends stopping outdoor activities if you feel unwell.
More information on the harms of wildfire smoke is here.