Southern Ontario hit with abnormal heat

Residents across southern Ontario — Toronto and Windsor in particular — are being confronted by temperatures approaching seasonal records as a warm air mass works its way into the region.

Temperatures around 40C with humidex value

Time in the pool may be in many people's plans Tuesday as temperatures soar well above seasonal values. (Darren Calabrese/Canadian Press)

Residents across southern Ontario — Toronto and Windsor in particular — are being confronted by temperatures approaching seasonal records as a warm air mass works its way into the region.

Weather explainer

The cause

CBC meteorologist Johanna Wagstaffe says the impending heat is because of a tropical air mass moving in from the Gulf of Mexico.

The effect

The humidex values are approaching dangerous levels for those with respiratory issues, for whom it's a "good idea to stay inside," Wagstaffe says.

The aftermath

A cold front from the upper Great Lakes will move into southern Ontario late Tuesday night and early Wednesday, bringing with it a cooling effect but also a risk of thunderstoms, Wagstaffe says.

Environment Canada has issued a humidex advisory in southern Ontario stretching from Windsor in the west to the Ottawa region in the east.

While temperatures will hover around the low 30s in the region Tuesday, humidex values near 40 C are predicted.

Heat alert issued for Toronto

Environment Canada has predicted a high of 32 C for Toronto, which would break the previous record high of 31.1 C on May 31, set in 1944. The historical average temperature for this date in Toronto is 21.6 C.

As of 2 p.m. Tuesday, the temperature in Toronto hit 29 C.

The City of Toronto, meanwhile, issued its first heat alert of the year Tuesday morning. A heat alert is issued when public health staff determine that weather conditions "suggest that the likelihood of a high level of mortality is between 25 and 50 per cent greater than what would be expected on a typical day."

During a heat alert, the public is encouraged to call or visit neighbours, family and acquaintaces who may be vulnerable to high temperatures. Affected groups include seniors, those with respiratory issues, the homeless, young children and people taking some kinds of medication.

Rising temperatures didn't seem to bother some in Toronto.

"Spring is the best time. The weather is very cool, especially in the morning," said Fazil Alli, who was riding his bicycle along Toronto's waterfront Tuesday morning. He said he's keeping cool the natural way. "When I sweat, my body's cool. When I ride my bicycle, I sweat. My body [gets] cool."

In Windsor, meanwhile, the temperature hit 32 C as of 2 p.m. The high there is expected to reach 34 C.

The weather system and the accompanying high temperatures are expected to arrive in the afternoon.

The agency said areas close to the Great Lakes will be up to 10 C cooler, which should provide relief for those looking for a respite from the heat.

The high temperatures won't last long, however, as a cold front is expected to sweep across southern Ontario Wednesday night and bring a return to seasonal norms.

While it will be hazy for much of southern Ontario, there are no smog warnings in effect.