The sticky humid air mass is expected to leave the region by Friday, which will lead to more comfortable temperatures on that day and into the weekend.
They planned to visit thousands more as the heat was expected to continue until Friday.
The move is part of the federal government's climate change adaptation in expectation of more frequent heat events. Low temperatures overnight will again be in the high teens to low twenties providing little relief from the heat.
However, daytime highs are still expected to be in the low 30s, with humidex values possibly reaching the low 40s. However, the daytime highs are still expected near 30 and overnight lows in the high teens.
The heat wave has hit the Atlantic provinces, too - a heat warning is in effect for Halifax as Nova Scotia has been experiencing temperatures of around 30 degrees, or up to 39 degrees with the humidex.More news: Samsung phones sent photos to random contacts, users say
Meanwhile, the the Middlesex-London Health Unit (MLHU) has prolonged their extended heat warning. "Both high and low temperatures are likely to be shaved by 10-15 degrees".
Environment Canada warns that extreme heat affects everyone.
Drouin says the victims fit the profile of people authorities describe as at risk: those with chronic illness or mental-health problems, people who live alone and people without air conditioning at home.
The Salvation Army was out at Gore Park handing out bottles of water reminding people to heed the warnings and protect themselves, and police have already received a number of calls including one on Appleby Line and Upper Middle Road in Burlington where they rescued a dog from a hot vehicle where the temperature was 66 degrees.