Ontario to expect severe thunderstorms on Tuesday, followed by a significant temperature drop

Published on May. 19, 2026, 10:11 AM

Updated on May. 19, 2026, 4:00 PM

A powerful cold front could bring damaging thunderstorms, heavy rainfall and a dramatic temperature drop to parts of southern Ontario before dawn Wednesday.

Southern Ontario’s summer-like warmth will come to an abrupt end later Tuesday, as a powerful cold front triggers another round of potentially severe thunderstorms across the province.

The threat will intensify throughout the afternoon and evening as heat and humidity rise ahead of the approaching front. Some communities may experience heavy rain, damaging wind gusts, and large hail before much cooler air arrives overnight. The chance for a tornado cannot be ruled out.

Compared to Monday’s more scattered storm activity, Tuesday’s setup appears more organized, particularly along the busy Highway 401 corridor and parts of southwestern Ontario. Forecasters say the atmosphere will be very moist, increasing the risk of torrential rain and rapidly changing conditions during the evening commute.

Be sure to stay up-to-date on any weather alerts or warnings in your area.

Storms ramp up late afternoon into Tuesday evening

The first thunderstorms are expected to form in the mid-to-late afternoon in areas near Lake Huron and Georgian Bay, including Barrie.

The focus will then shift south and east throughout the evening as a more organized line of storms moves along the 401 corridor from the GTA to London, Windsor and Sarnia. The strongest storms are most likely to hit southwestern Ontario, where the line may remain more intact as it moves eastward.