‘Long-awaited’ reprieve as multi-day heat warning lifts for Waterloo Region
Posted Jul 17, 2025 05:31:21 AM.
Last Updated Jul 17, 2025 10:25:10 AM.
After six days of a brutal heat warning in Waterloo Region and across southern Ontario, it appears as though some relief may be on the way.
Environment Canada issued an extended heat warning last Friday, warning of hot and humid conditions stretching all the way into July 17.
That warning ended on Thursday morning around 5 a.m.
Hot conditions throughout the week were also combined with poor air quality due to wildfires burning in northern Ontario, bringing air quality health index levels into the low end of the high-risk zone.
“The long-awaited cold front is crossing southern Ontario, along with it some scattered showers and the risk of a thunderstorm,” said 570’s Weather Specialist Allister Aalders. “Nothing too widespread, and it’s going to be a fresher air mass settling in 11 C overnight and then Friday, 25 C. The humidex is only 27.”
Temperatures for Thursday are expected to reach 25 C with a humidex of 32.
Aalders mentioned it will be a much-needed break, but it could bring some rain and potential thunderstorms along into the weekend.
“The weekend could be a bit unsettled. We’ll have a mix of sun and cloud both Saturday and Sunday, but Saturday afternoon or evening, some showers are likely to develop, and that will come with the risk of a thunderstorm,” he noted.
Some good news alongside the drop in overall temperatures is the hand-in-hand decline in humidex values heading through Friday and into the weekend. Aalders said, though, that it may begin rising back up heading towards next week.
“While we get a break from this oppressive humidity as we go through tonight and Friday, those dew point values which measure the moisture in the air coming down into a comfortable range, the humidity will start to build back in a bit this weekend although not as oppressive feeling into the low thirties with actual air temperatures more so in the mid twenties.”
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Much-needed relief both outdoors & indoors
Experts are saying the break in the heat wave is incredibly needed throughout the region as families continued to struggle throughout the week with handling those increased temperatures.
It comes as new data coming through the University of Waterloo is showing temperatures can be just as harmful when they climb indoors through those same lingering heat waves.
“What we want the public to be able to do is to better survive and go through these extreme heat waves,” said Dr. Plinio Morita, Associate Professor with the School of Public Health Sciences at UW. “We usually consider our homes our safe environment, our safe place to run away from these extreme heat events. What the data is showing us is that you need to be careful even inside your own home.”
Morita mentioned that the university has begun to look at and develop a threat scale depending on the length and temperatures which people are being exposed to those heightened temperatures.
“The levels are based on temperature thresholds,” Morita said. “If you look at the definitions, usually a level one threat is triggered when people are exposed to over eight hours of temperatures over 26 C inside their own homes. A level two threat is triggered when exposure hits eight hours of over 31 C.”
Full clip from Dr. Plinio Morita, Associate Professor with the School of Public Health Sciences at the University of Waterloo on temperature thresholds.
Researchers from the Ubiquitous Health Technology Lab (UbiLab) at UW used smart thermostats with Wi-Fi connectivity, using them to collect indoor temperature data across North America spanning from 2015 to 2024.
The team stated that it’s an important endeavour in order to raise attention on the heat-related health risks that grow when temperatures climb indoors. They said those risks can become severe and even deadly, particularly for vulnerable portions of the population.
“Depending on the specific user population and target population, older adults especially lose the ability to self-regulate and self-monitor their body temperature. When temperatures start rising, they don’t notice that, and they face exposure inside their own homes.”
Morita stated that it’s all about saving lives, with the team’s research showing some dire consequences if nothing is addressed.
“The reason why this project is so important is because if you look at the extreme heat storm that we had in the summer of 2021 in British Columbia, for example, we saw over 619 deaths in B.C. alone, and 98 per cent of them occurred inside their home.”
