Environment Canada says a multi-day heat event is continuing, with daytime highs of 32 to 35 C and humidex values between 37 and 42. Overnight lows are expected to remain between 20 and 23 C.
The heat is forecast to last through Tuesday for most areas, although eastern Ontario and the Greater Toronto and Hamilton Area could see hot and humid conditions persist into Wednesday. A cooler air mass is expected to arrive Tuesday night.
Officials warn that the hot, humid air could also lead to deteriorating air quality, with the Air Quality Health Index possibly approaching the high-risk category. They urge residents to watch for signs of heat exhaustion, such as headache, nausea, dizziness, thirst, dark urine and fatigue, and to seek immediate medical attention for signs of heat stroke, including red or hot skin, confusion, or changes in consciousness.
Environment Canada advises staying hydrated, keeping living spaces cool, checking on vulnerable individuals, and avoiding leaving children or pets in parked vehicles. Heat warnings are issued when high temperatures or humidity pose an elevated risk of illnesses such as heat stroke or heat exhaustion.
The agency encourages the public to monitor alerts and forecasts, and to report severe weather via email to ONstorm@ec.gc.ca or on X using #ONStorm.
