TORONTO — Environment Canada says a storm that toppled trees and downed power lines across southern Ontario on Wednesday became more powerful than expected because of the time of day at which it occurred and the conditions that prevailed at the time.
Senior Climatologist David Phillips says the storm would likely have passed with much less notice if the cold front that caused it had struck earlier in the day, when temperatures and humidity levels were lower.
But when the cold front passed over the southern part of the province during the mid to late afternoon, Phillips says it encountered warm, moist air that gave the storm an additional boost.
Environment Canada received reports of uprooted or damaged trees around Lake Erie, in pockets throughout the Greater Toronto Area and in Algonquin Park.
Local bands of hail and heavy rain caused flooding in some cases, including Toronto's landmark Eaton Centre, where water gushed from the roof into the mall.
Provincial utility Hydro One reported that at one point as many as 47,000 customers were without power thanks to damage to local lines.
Phillips said there was nothing unusual about the cold front that began racing across the region at around 3 p.m., but said the conditions it encountered on its path were what ultimately made the difference.
"If it came at four in the morning it would wake you up, but it wouldn't necessarily have as much energy associated with it," he said.
When the front reached the Toronto area at around 4 p.m., for instance, Phillips said Environment Canada recorded temperatures of 29 C with humidex levels of around 36.
Extra heat and moisture have the effect of energizing cold fronts, he said, increasing the impact of the changing weather conditions.
In the Ontario towns of Jarvis and Waterford, Environment Canada reported several instances of tree being torn apart or ripped from their roots altogether. The agency reported one house had tree branches embedded in the roof while a porch and nearby barn were destroyed by falling debris.
Nickel to quarter-sized hail was also reported in the area.
In the Lake Erie region, a team of meteorologists from Environment Canada will be assessing damage.
In Toronto, shoppers seeking refuge from the rain at the downtown Eaton Centre found the elements had followed them indoors. Images shared on social media showed water pouring from the roof as shoppers tried to go about their business on Wednesday afternoon.
A spokeswoman for mall operator Cadillac Fairview says a water leak, believed to have been caused by the rain, started on the third level of the shopping centre at about 4:30 p.m. and flowed down to the lower levels.
Michele Enhaynes said mall staff identified the source of the leak and closed off parts of the shopping centre. Retailers such as Ted Baker, Guess, Marciano and Massimo Dutti had to close prematurely as a safety precaution, she said.
Michelle McQuigge , The Canadian Press