A very strong line of thunderstorms developed over Sarnia late Saturday morning and tracked northeastward over Southern Ontario towards Ottawa.
Environment Canada reported damaging winds over a large swath of Southern Ontario.
There were five fatalities reported across the province and a few others injured.
In Brampton, Peel Regional Police reported that a large tree had struck a woman who was walking in the storm at around 1:30 p.m. The woman was transported to a local hospital where she later died.
OPP reported that shortly before 12:30 p.m., three people were taken to hospital after a tree fell on a camping trailer at Pinehurst Lake Conservation Area near Cambridge. One of the individuals died after suffering serious life-threatening injuries while the other two had minor injuries, police said.
A 44-year-old man was also killed in Greater Madawaska, west of Ottawa, after reportedly being struck by a falling tree.
On Saturday evening, one person in Ottawa's west end had died after suffering “major injuries.”
Later Saturday, Gatineau police said a 51-year-old woman drowned after her boat capsized in the Ottawa River.
There was also extensive damage to trees, power lines and buildings, overturned cars as well as widespread power outages.
Peak wind gusts reached 132 kilometres an hour at the Kitchener-Waterloo Airport and 120 kilometres an hour at Toronto Pearson International and Ottawa international airports.