Southern Ontario is dealing with intense heat and humidity, but most areas are unlikely to break daily temperature records this week.
Even though the region is under an orange heat warning, the bigger concern is not one extremely hot day. Instead, meteorologists are warning that the length of this heat wave could create serious health risks.
According to Peter Kimbell, a warning preparedness meteorologist with Environment and Climate Change Canada, temperatures may be uncomfortable and dangerous, especially for vulnerable people.
Most Areas Will Not Break Heat Records
Many residents may feel like the current heat deserves record-breaking status. However, Kimbell said the numbers show that most communities in southern Ontario will likely fall short of daily heat records.
Forecast highs are expected to reach between 34 C and 37 C under the orange heat warning.
Windsor may be the exception. A forecast high of 37 C on Canada Day could be enough for the city to break a daily temperature record.
Duration Is the Main Concern
While the temperatures are high, Kimbell said the real issue is how long the heat will last.
He explained that southern Ontario is expected to face four consecutive days of extreme heat. That extended stretch is what makes the situation more concerning.
According to Kimbell, a heat wave lasting more than three days can have a stronger impact on public health and daily life than a single hot afternoon.
Why the Warning Was Upgraded to Orange
Environment and Climate Change Canada upgraded the alert to an orange heat warning because of the expected duration and possible health effects.
The colour-coded warning system was introduced late last year, and many Canadians are still becoming familiar with it. Orange warnings are intended to be rare and are used when weather conditions could cause major disruption, damage, or health impacts.
Kimbell said that when heat lasts longer than three days, officials may consider raising the warning level if the expected impact is serious enough.
Humidex Could Make It Feel Like 44 C
Humidity will make the heat feel even worse. In some areas, the humidex could make conditions feel closer to 44 C.
Another concern is the lack of overnight cooling. Toronto could see nighttime lows drop only to around 24 C for two nights in a row. That is about eight degrees above normal.
Without cooler nights, the body has less time to recover from daytime heat, increasing the risk of heat-related illness.
Vulnerable People Need Extra Support
Kimbell urged residents to check on people who may be more vulnerable during extreme heat.
This includes older adults, people with health conditions, people without reliable cooling, and anyone living in difficult conditions.
He said people in vulnerable situations may need extra help when temperatures become this high.
What Is Causing the Heat Wave?
The current heat wave is being driven by a ridge of high pressure over the southern and central United States.
This weather pattern is pushing hot, humid air across the Great Lakes and into Ontario, creating uncomfortable and potentially dangerous conditions across the region.
Kimbell described the weather simply as “hot and uncomfortable.”
How Common Are Heat Waves Like This?
According to Kimbell, heat waves lasting several days are not extremely rare in Ontario.
He said that every couple of years, the province experiences a stretch of at least three days with temperatures above 34 C or 35 C.
Still, the combination of high humidity, warm nights, and several consecutive days of heat can create serious risks.
Ontario’s Worst Heat Wave Happened in 1936
Kimbell also referred to Ontario’s most severe heat wave on record, which occurred nearly 90 years ago.
In July 1936, before the humidex was used, Toronto reached 40 C for three straight days. That deadly heat wave killed more than 200 people.
Kimbell said the current heat wave does not come close to that historic event, but it is still serious enough to require caution.
Another Heat Warning Could Return Next Week
The current heat may not be the end of southern Ontario’s hot weather pattern.
Kimbell said weather models suggest another heat warning could appear next week. If that happens, the prolonged heat could become even more difficult for residents to manage.
Southern Ontario’s current heat wave may not break many daily temperature records, but its length and humidity make it a serious concern. With four straight days of extreme heat, humidex values near 44 C, and limited overnight relief, residents are being urged to take precautions and check on vulnerable people.
While Windsor may set a Canada Day record, the broader danger comes from prolonged exposure. Another possible heat warning next week could make conditions even more challenging.