A warm humid air mass and temperatures in the low 30s have combined to create a wilting summer heat that will smother much of southern Ontario for the next several days, baking Waterloo Region and Wellington County in sweltering temperatures that feel like the low 40s.

Environment Canada predicts humidex values could reach 40 to 42 Monday for much of southern Ontario, including Waterloo Region, as well as Wellington and Brant Counties.

Communities along the rim of the Great Lakes could fare a little better according to the weather agency, where the lake breeze is expected to cool things off, but humidex values will remain in the 37 to 39 range.

A change in the weather pattern is not expected until Friday, when Environment Canada says humidex values will drop below 40.

Temperatures will cool off Saturday, Sunday when the high hits 24 and 23 degrees.

Potential severe weather on tap

This week's bout of searing temperatures also carry a chance of severe weather through much of the week, according to Environment Canada.

Its predicted Monday will see a low chance of thunderstorms for an area extending west from Hamilton to Grand Bend, especially along the shores of Lake Erie.

Environment Canada warns any storm developing Monday could produce torrential downpours with rainfall amounts near 50mm.

The potential for torrential downpours are also predicted Tuesday, with Environment Canada calling for a chance of thunderstorms over much of southern Ontario.

The storms could produce torrential downpours with rainfall amounts near 50mm.