Canada

Photo: The Canadian Press. All rights reserved.

A woman cools down in the water sprinklers at Dundas Square as they take in the extreme heat in Toronto on Tuesday, June 19, 2012. Environment Canada has issues a heat alert for the next few day in Southern Ontario and Toronto. THE CANADIAN PRESS/Nathan Denette

Smog added to the misery in southern Ontario on Wednesday as a wide swath of central Canada sweated out the second straight day of scorching weather.

The hot spell coming in from the U.S. has pushed the mercury from southwestern Ontario through to Quebec City to the low 30s, but it feels more like 40 degrees or more due to soaring humidex values, Environment Canada said. Cooler air is forecast to drop temperatures down into the 20s starting Friday.

Smog advisory are in effect from Windsor to Kingston, and special heat alerts or heat warnings have been issued in several municipalities across the region, including Toronto, where cooling centres have been opened for people vulnerable to hot temperatures.

Children, seniors and those with disabilities and chronic illnesses are most at risk during hot weather like this, said Paul Buttery, environmental health specialist for Lambton County in southwestern Ontario.

Lambton County and the City of Sarnia have eight designated areas for people to take refuge from the heat, though Buttery said so far he hasn't heard of a jump in the number of people seeking emergency help for heat exhaustion, which can occur after several days of exposure to hot weather.

If you're coming down with heat exhaustion, Buttery said, then "the best thing to do is stop all activity and seek a cool place, drink water and seek medical attention immediately if your symptoms worsen."