Before and after: Smoky haze takes over Toronto

These photos were taken just one day apart, showing how quickly Toronto's sky went from clear to smoky. Smoke from forest fires in northwestern Ontario is causing poor air quality and reduced visibility for much of southern Ontario, according to Environment Canada, which says the conditions may last until Friday morning. The agency is urging people to 'reschedule or cancel' outdoor activities.

Before and after: Smoky haze takes over Toronto These photos were taken just one day apart, showing how quickly Toronto's sky went from clear to smoky. Smoke from forest fires in northwestern Ontario is causing poor air quality and reduced visibility for much of southern Ontario, according to Environment Canada, which says the conditions may last until Friday morning.

The agency is urging people to 'reschedule or cancel' outdoor activities.