Elevated levels of pollution are forecast for Sarnia today for a second straight day.
The air is expected to reach 6 on the air quality index this afternoon and into this evening, which is in the moderate risk range.
At that level, people with heart or breathing problems should consider reducing or rescheduling strenuous outdoor activities, or anyone if they are experiencing symptoms, the Ministry of the Environment, Conservation and Parks says.
Sarnia and Windsor are only areas of the province expected to reach an AQI of 6 today.
The air quality index is based on provincial monitoring for ozone, fine particulate matter, and nitrogen dioxide.
On Monday, Sarnia’s AQI reached 5 for a few hours in the early afternoon and fell to 3 overnight.
The ministry says more than 50% of Ontario’s ground-level ozone and fine particulate matter come from the U.S. Midwest, with local pollution sources contributing to the severity of smog events.