'Significant heat wave': All of southern Ontario under heat warning

CTV Kitchener: Aug. 8 weather update This week's heat wave could be the longest and most significant we've seen so far this year. Lyndsay Morrison has details.

This week could bring southern Ontario its “longest and most significant heat wave of the summer so far,” Environment Canada said Monday.

With daily highs above 30 C and humidex values near 40 expected for much of the work week, all of southern Ontario has been placed under a heat warning.

A heat warning was also issued for nearly the whole area for several days last week, with the Bruce Peninsula as the lone exception.

This time around, Environment Canada says, humidex values will rise to the mid-30s on Tuesday before more humid air moves in, bringing potentially dangerous heat and humidity from Wednesday through Friday.

Additionally, the agency is warning of relatively “warm, muggy” conditions at nighttime this week, with temperatures expected to fall below 20 C rarely if ever starting Tuesday night.

Temperatures are expected to cool down somewhat by the time the weekend rolls around.

Forecasts for Waterloo-Wellington call for a high of 31 C on a sunny Tuesday with humidex making it feel more like 33, followed by highs of 32 C and 33 C and increasing humidity on Wednesday and Thursday respectively.