05/31/2011 11:47 EDT | Updated 07/31/2011 05:12 EDT

Ontario Approaching Seasonal Heat Record

(CBC) Residents across southern Ontario — Toronto and Windsor in particular — can expect temperatures approaching seasonal records on Tuesday as a warm air mass works its way into the region.

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, 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.

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.

As of 10 a.m. Tuesday, temperatures in Windsor had already hit 28 C, with a reading of 37 C with the humidex factored in. The high there is expected to hit 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.