A significant heat event is expected to build across southern Ontario next week, including Toronto, with humidex values potentially reaching the low 40s, according to The Weather Network.
In a report released Thursday, the network warned that a heat dome developing over the United States will push temperatures across southern Ontario and the Greater Toronto Area into the 30s on most days.
The heat is expected to begin Sunday and persist throughout the week. According to The Weather Network, daytime highs will generally range from the low to mid-30s. However, on days such as Canada Day, the humidex could make it feel like temperatures are in the low 40s.
The Weather Network says Canada Day could mark the peak of the heat event.
With many people planning to spend time outdoors for Canada Day celebrations, whether at the beach, hosting barbecues, or attending community events, Torontonians are being urged to take precautions against heat-related illnesses by staying hydrated, limiting strenuous outdoor activity during peak afternoon hours, and seeking shade or air-conditioned spaces when possible.
The network explains that heat domes are stationary areas of high pressure that trap hot air beneath them, leading to prolonged periods of above-seasonal temperatures.
The heat may not be the only challenge next week. Forecasters are also monitoring the potential for thunderstorms throughout the week as heat and humidity continue to build.
The expected weather marks a dramatic shift from recent conditions, with below-seasonal temperatures and frequent rainfall dominating much of the past several weeks, disrupting many outdoor activities and events.
The upcoming heat aligns with recent seasonal outlooks. Environment Canada has forecast a warmer-than-normal summer across much of the country, with higher temperatures expected compared with seasonal averages.
Environment Canada’s Toronto forecast also shows the city warming sharply into next week, with highs of 32 C on Tuesday and 33 C on Canada Day, along with a chance of showers or thunderstorms. The agency lists Toronto’s seasonal normal for this time of year at 26 C, meaning next week’s daytime highs could sit several degrees above average.
Heat warnings for southern Ontario are generally issued when two or more consecutive days are expected to reach daytime highs of at least 31 C with nighttime lows of 20 C or warmer, or when humidex values are expected to hit 40 or higher for at least two days, according to the City of Toronto.
For safety context, Toronto’s Heat Relief Strategy focuses on reducing heat-related illness and death, particularly among vulnerable groups. The city advises residents to monitor local alerts, use cooling spaces when needed and check Environment Canada or the WeatherCAN app for updated warnings.
