Rounds of thunderstorms impact Ontario during warmest week of the year so far
Southern and eastern Ontario will experience unseasonably warm temperatures nearing 20°C this week. However, the warmth brings moisture-fuelled storms, with heavy rain and rounds of thunderstorms expected through Wednesday
Southern and eastern Ontario will experience a mild week, but it will be marked by multiple rounds of thunderstorms and periods of heavy rain.
Potential impacts include frequent lightning, small hail, and water pooling on roads, which may affect travel conditions. The clash between colder air to the north and mild air in the south is driving this active weather pattern.
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Special weather statements and yellow-coded rainfall warnings are in effect.
Weather Highlights:
Southern and eastern Ontario will experience daytime highs in the high teens to above 20°C this week
Thunderstorms move through the region Tuesday, bringing heavy downpours, lightning, and small hail. Wednesday and Thursday continue the stormy trend
Water will likely pool on roads and in low-lying areas. Don't drive through flooded roadways
Strong thunderstorms and heavy rain hit southern Ontario through Wednesday
A surge of warm southerly air is set to dominate southern and eastern Ontario this week, with daytime highs reaching the high teens to above 20°C—temperatures more typical of late May than mid-April. Strong southwesterly winds, gusting up to 60 km/h, will accompany this warmth, alongside moisture-rich systems drawing energy from the Gulf of Mexico.
Tuesday: Thunderstorms tracked along Lake Huron shores and across southwestern Ontario on Tuesday morning, impacting the morning commute in the Greater Toronto Area (GTA), as well.
Heavy downpours and frequent lightning were reported.
Rainfall totals could reach 30-50 mm near Goderich, London, and Sarnia, with 20-30 mm likely for areas spanning the GTA to Niagara.
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Tuesday afternoon and evening will remain mild, with a chance of a passing storm.
Windsor will try to set another benchmark for the warmest temperature in Canada for 2026, with a high of 28°C forecast.
Forecasters are also monitoring the potential for isolated thunderstorms with severe weather potential in the southwest later in the evening.
Wednesday: A similar weather pattern unfolds, with overnight storms originating in Michigan progressing into southern Ontario. Heavy downpours, frequent lightning, and small hail are possible.
Conditions remain uncertain for the afternoon as a warm front may lift thunderstorm ingredients northward. Areas such as Windsor, Lake Erie, and London could see storm development depending on the timing of the front.
If it is delayed, the afternoon and evening may remain cloudy, showery with mild conditions.
Thursday: Warm, elevated showers and thunderstorms persist as the warm front shifts northward.
Rain totals for the week could reach between 50-120 mm.
The saturated ground has reduced ability to absorb further rainfall, warns Environment and Climate Change Canada (ECCC), adding that water will likely pool on roads and in low-lying areas.
The Toronto and Region Conservation Authority (TRCA) extended its flood outlook on Monday afternoon, cautioning that heavy rainfall over a short period could lead to localized flooding in affected areas.
Daytime highs soar above seasonal norms
Temperatures will consistently remain 10°C above seasonal norms, with Toronto's Pearson International Airport forecast to record five or six consecutive days near 20°C this week.
Typically, Pearson airport averages fewer than three days above 20°C in April. However, mid-April 2023 saw more intense warmth, with temperatures climbing to 29.4°C on April 12, setting a notable benchmark for this time of year.
Strong winds and temperature drop expected this weekend in southern Ontario
A strong cold front will move across the region Saturday night into Sunday, bringing very windy conditions and a sharp drop in temperatures. By Sunday, daytime highs will hover in the single digits, with flurries expected, including potential lake-effect flurries east of Lake Huron and Georgian Bay.
Early next week is forecast to resemble late March, with changeable temperatures throughout the final week of April. Near-seasonal to cooler-than-seasonal conditions are anticipated to persist into early May.
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Stay tuned to The Weather Network for the latest forecast updates across southern Ontario.