Townhouse units were destroyed in a fire and several roads became shallow streams when stormy weather rolled through southern Ontario overnight.

After days of hot and dry weather, severe thunderstorms brought heavy rain, strong winds and intense lightning strikes that are being blamed for a fire that engulfed townhouses in Brampton.

Fire officials said four townhouse units were destroyed and two others were damaged when the fire broke out at a complex on Spadina Road in Brampton late Wednesday night. Residents reported hearing a loud bang when lightning struck a roof, and they scrambled out of the home without any injuries.

The roofs of four units collapsed as about 50 firefighters battled the blaze.

No injuries were reported, but the fire has displaced about 18 people.

Damage is estimated at $1 million.

In Vaughan, lightning struck a home on Amalfi Court, near Martin Grove Road and Highway 7. Firefighters were able to quickly extinguish the roof fire before flames spread. The home's residents were allowed to return within hours.

Higher-than-normal positive lightning strikes

The damage is due to a higher-than-normal percentage of positive lightning strikes during the storm, said a warning preparedness meteorologist with Environment Canada.

Positive strikes are stronger and carry more of a charge, and so they're more likely to cause damage on the ground, said Geoff Coulson.

There were 748 lightning flashes within 50 kilometres of the CN Tower, and about 14 per cent of those were positive, he said.

Normally, just five per cent of lightning strikes are positive.

Because of that, Coulson said such damage as was seen in Brampton is rare.

"But every year we've seen it," he said. "Some of these storms can occur anywhere in the province."

Elsewhere in Vaughan, four vehicles became stranded in more than a metre of water when the intersection of Bowes Road and Rivermede Road flooded. Firefighters were called in at about 2:30 a.m. to help people out of the vehicles.

After the overnight deluge, the Toronto and Region Conservation Authority is warning people to be cautious near swollen and fast-moving rivers and streams.

The storm brought some of the only rain the GTA has seen this month. July's average at Pearson International Airport is 74.4 millimetres, and this month's recorded rainfall is now about 60 millimetres.

Flooding disrupts GO Transit service

The storm's aftermath also caused problems for commuters who take trains on GO Transit's Richmond Hill line.

Service was suspended for more than an hour because a section of track was under water, cancelling two train trips to Union Station.

Service resumed with the 7:25 a.m. train, but riders experienced delays of 15 to 25 minutes.

At one point, shuttle buses were operating between Richmond Hill and Unionville GO stations, and GO Transit was encouraging riders to find an alternate route.

More rain possible, Environment Canada says

Meanwhile, people should keep their umbrella within arm’s reach.

After the overnight storm, there is a chance of more showers and thunderstorms Thursday afternoon and evening, Environment Canada said.

Thursday will be cloudy with a high of 28 C.

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With files from The Canadian Press

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