Lightning strikes the CN Tower during a summer storm. (Submitted by Stephen Pereira)

About 2,000 Toronto Hydro customers were still without electricity Monday after thunderstorms swept across southern Ontario on Sunday night.

About 21,000 people lost power at the height of the storm.

By noon Monday, of the 2,000 without power, 1,500 were in suburban York Region.

About 4,657 customers were still without power across the province as of 5:15 p.m. ET, according to Hydro One.

Pearson International Airport also lost power briefly before generators kicked in, and some flights were cancelled because it was unsafe for workers to be working on the tarmac during a lightning storm.

The death of a woman near Sarnia, Ont., has been blamed on the storm.

Virginia Baldwin, 49, died after being struck by lightning while taking shelter under a dinghy on a beach north of Sarnia.

The main problem in Toronto, according to the utility, is downed power lines and fallen trees.

"Our crews so far have removed 16 trees that have come down altogether. Of course we have to clear all that away with chainsaws before we can get on restoring the power, and putting the poles and lines back up, so that's what's taking the time," said Toronto Hydro spokesman Blair Peberdy.

A concert by the Alberta band Nickelback at Toronto's Molson Amphitheatre was also cancelled because of the weather.

Environment Canada had issued a severe thunderstorm watch for Toronto late Friday afternoon.

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