Environment Canada says smoke plumes from wildfires in northeastern Ontario will continue to blanket the region for a third day.
That means high levels of air pollution will continue to cause eye and throat irritation and even worse health problems for those who are susceptible.
Canada Post has gone to a "yellow" service alert, which means mail delivery has resumed, but there may be delays due to the air quality. A "red" alert yesterday meant that couriers were pulled off their routes completely.
Ontario Air Quality assessed the risk as "moderate" over Windsor on Thursday morning, but that was expected to become a "high" risk later in the day and evening.
"Air quality and visibility due to wildfire smoke can fluctuate over short distances and can vary considerably from hour to hour," read Environment Canada's statement.
On Wednesday, the city was "very high" on the provincial index, indicating residents should stay inside.
Those with lung or heart disease, older adults, children, pregnant people, and those who work outdoors are most at risk of illness related to wildfire smoke.
"If you have an HVAC system in your home, use the highest-rated MERV filter for your system," advised Environment Canada. "You can also use a portable HEPA air cleaner. Keep your doors and windows closed if the temperature in your home is comfortable."
For those who work outside, the agency recommends a well-fitted respirator-type mask.
"Respirators do not reduce the exposure to gases in wildfire smoke. It is important to listen to your body and reduce or stop activities if you are experiencing symptoms," said Environment Canada.
The City of Windsor has opened several public spaces to those who need a reprieve from smokey air.
In the downtown area, the Windsor International Aquatic and Training Centre, Windsor Public Library Central Branch, the Homelessness and Housing Help Hub, and the Chimczuk Museum will be open during the day.
Elsewhere in the city, residents can get a break at the Adie Knox Herman Recreation Complex, Optimist Community Centre, Gino and Liz Marcus Community Complex, Forest Glade Community Centre, Capri Pizzeria Recreation Complex, Constable John Atkinson Memorial Centre, and the WFCU Centre.
Residents should call 311 for more information.