The City of Toronto issued a heat alert on Tuesday as a three-day heat wave descended on southern Ontario.

A blanket of heat and humidity reached the city early Tuesday morning, blasting temperatures and humidex values sky high.

The temperature in Toronto had already reached 30 C by noon. With the humidity, it felt more like 39 C in many areas of the city.

The temperature was expected to reach as high as 32 C by Tuesday afternoon while humidex levels were forecast to reach 40 C and higher.

Environment Canada warned southern Ontario that elevated humidity levels were expected to continue through Thursday, making for uncomfortable conditions.

Night-time temperatures during the three-day heat wave are not expected to offer much reprieve for southwestern Ontarians. The temperature is not expected to drop below 22 C during the night in most areas.

Environment Canada is suggesting residents stay in an air conditioned place and seek shade whenever possible during the heat event.

During a heat alert, residents are encouraged to stay out of the heat and drink lots of fluids. It is also suggested that residents check on family and friends, especially isolated seniors and those with chronic illnesses.

A Friday cold front is expected to cool much of the area, but temperatures are only expected to drop into the mid-20s in the Toronto area.