Severe thunderstorms, extreme humidity, and potential tornado risks across Ontario this week

Environment and Climate Change Canada launched a new thunderstorm outlook on Monday, warning Ontario residents of severe weather risks over the next four days. The forecast predicts scattered showers, severe thunderstorms, and potential tornado activity, following Monday’s unusually warm temperatures of 30 C in Windsor and 27 C in the GTA and Ottawa Valley. Meteorologist Geoff Coulson noted that while Monday’s weather appears stable, heat and humidity will build through the week. A southwesterly wind will introduce an unstable air mass, bringing showers and thunderstorms to southwestern Ontario by Tuesday late morning. The GTA may experience storms in the late afternoon or early evening, with activity spreading eastward into eastern Ontario by Wednesday morning. Scattered showers and thunderstorms are expected to persist through Thursday and Friday, though not all-day rain. Coulson warned of brief relief during storms, followed by intensified heat and humidity afterward. A more organized weather system, originating from Michigan, is expected to reach southwestern Ontario late Thursday or overnight Friday, potentially affecting Toronto by late Thursday evening or early Friday. Heat warnings may be issued for parts of Ontario on Wednesday and Thursday, with Windsor facing criteria of two consecutive days above 31 C and nighttime lows above 21 C. Humidex warnings of 42 or higher in southwestern Ontario—or 40 elsewhere—are also possible. Coulson advised residents to monitor Environment Canada watches and warnings, as conditions may develop into severe storms or tornadoes later in the week.