July 2025 is shaping up to be one of the hottest and most humid months on record across Ontario, aligning with the latest forecasts from Environment Canada and The Weather Network. If you’re planning a getaway, outdoor concert, or cottage escape this month, get ready for more than just typical summer heat—intense warmth and sudden storms are on the horizon.
Where the heat will hit hardest in Ontario
Southern Ontario, including cities like Toronto, Windsor, and London, will bear the brunt of this summer’s extreme heat. Daytime highs are expected to stay well above seasonal averages, and persistent humidity will keep nights feeling sticky and uncomfortable. In places like Windsor and parts of southwestern Ontario, humidex values could exceed 40 °C (104 °F), creating conditions that feel downright tropical.
Even in Northern Ontario, communities such as Thunder Bay and Sault Ste. Marie are forecast to see above-normal temperatures. Thunder Bay could experience prolonged dry periods, while regions further east, such as Sudbury, may see frequent humidity-fueled thunderstorms.
Heat will arrive in waves, with occasional breaks
While extreme heat is expected to dominate the pattern, forecasters anticipate some temporary cooling periods offering brief relief. These heatwaves will shift between regions, meaning no single area is likely to endure non-stop scorching conditions all month long.
Precipitation levels will remain near normal across much of the province, but summer storms will be highly localized and sometimes severe. One community could see heavy downpours, while a neighbouring town remains completely dry. The Greater Toronto Area will also experience this spotty, unpredictable storm activity, with some areas missing rainfall entirely.
Wildfire risk lingers in the north
A growing concern in Northern Ontario is the heightened wildfire risk, especially in regions northwest of Lake Superior. Prolonged periods of hot, dry air could create the ideal conditions for fires to ignite and spread. Smoke from these events may drift into the southern parts of the province, potentially reducing air quality in cities like Toronto for multiple days at a time.
Expect sun, humidity, and pop-up storms
After a June filled with cool mornings and rainy weekends, summer has fully settled in across Ontario. The province now sits in a 70–90% probability zone for above-average temperatures through to September. Southern and eastern regions will see more frequent thunderstorms, but also plenty of sun between systems.
July 2025 is quickly becoming one of the most memorable summer stretches in recent years—with intense heat, lingering humidity, and the sudden burst of storms all making their mark.
