Environment Canada has issued a special weather statement warning of a prolonged hot and humid period in much of southern Ontario.
Very warm air is expected to arrive Monday, while the extreme heat and humidity is expected to intensify and last for much of the week.
Temperatures are expected to sit around 30C on Monday, soar well into the 30s Tuesday and stay hot through Thursday.
With high levels of humidity in the forecast, it is expected to be hot and uncomfortable around much of the Greater Toronto Area, where temperatures could feel warmer than 40C with the humidex.
People are being advised to stay in air-conditioned places or seek shade whenever possible.
Drinking lots of water and limiting strenuous physical activity is also recommended.