An intense heat wave is sweeping across Southern Ontario this first weekend of July, with oppressive humidity levels and daytime highs reaching 33°C (91°F). According to Environment Canada, little to no relief is expected until Sunday night, placing heavy strain on densely populated regions such as Toronto, Mississauga, Brampton, Halton Region, Hamilton, Niagara Region, and Durham Region.
Heat warning in effect for Toronto, Hamilton and surrounding areas
Daytime highs are forecasted between 31 and 33°C (88–91°F), with overnight lows remaining uncomfortably warm, ranging from 21 to 25°C (70–77°F). This lack of overnight cooling is especially dangerous in urban zones where the heat island effect is strongest. With the humidex likely exceeding 40, conditions will remain stifling well into the evening hours.
Air quality and public health in focus
The combination of high humidity and extreme heat is expected to deteriorate air quality, with the Air Quality Health Index approaching high-risk levels, particularly for seniors, young children, and individuals with pre-existing health conditions. Public health officials are issuing renewed warnings, urging people to watch for symptoms of heat exhaustion such as headaches, nausea, dizziness, extreme fatigue, and dark-coloured urine. In the case of heat stroke, which is a medical emergency, symptoms may include confusion, red or hot skin, and loss of consciousness. Call 911 immediately and begin cooling measures while waiting for medical assistance.
Sweltering conditions to persist through Sunday evening
Forecasts indicate no significant drop in temperature before Sunday night, when a slight cooling trend may begin. In the meantime, local authorities continue to monitor conditions, urging residents to stay hydrated, keep blinds closed during the day, limit time outdoors during peak sun, and make use of public cooling centres if necessary.
