Environment Canada is warning air quality across parts of Toronto and surrounding areas could deteriorate tonight as expected Diwali fireworks combine with stagnant weather conditions.
A spokesperson for the agency says temperatures are expected to be colder tonight at ground level compared to the air above.
As a result, firework smoke could stay closer to the ground rather than mix in the atmosphere, leading to a possible air quality deterioration.
The special air quality statement says Toronto, Brampton, Mississauga and the surrounding areas could be impacted, with the agency warning people with smoke sensitivities to consider taking steps to reduce their exposure.
The spokesperson says it's believed to be the first time an air quality statement has been issued in relation to holiday fireworks, in part because similar atmospheric conditions during last year's Diwali celebrations led to elevated air quality risks.
Mississauga and Brampton allow some fireworks on private property without a permit on Diwali, but Toronto requires residents to get a permit.