The blackouts were caused by powerful wind storms that swept through seven eastern U.S. states late Friday, toppling trees and branches into power lines and knocking out big transmission towers and electrical substations.
U.S. officials feared the death toll, already at 23, could climb because of the heat and widespread use of generators, which emit fumes that can be dangerous in enclosed spaces.
About 200 Hydro One employees from Ontario are helping local utilities in Baltimore, Virginia, and Washington areas. Hydro Quebec has about 70 workers assisting local crews in Maryland.
Bill Smeaton, of Hydro One, says the Ontario team expects to be in the Washington area until at least Saturday.
"The type of damage is very similar to what we see in our cottage country after some of those micro bursts that we get," says Smeaton, a Hydro One distribution superintendent for Georgian Bay, Ont., who contributed to power restoration in Florida in 2005 and again in Vermont last year following hurricane Irene.
The most worrisome factor about this storm, he says, is the fact that the damage is in a dense urban area.
"Having that much damage right in your city centre's a lot trickier to deal with," he says.
That, he says, is making it hard for Pepco, the local utility company, to get a firm tally on damages.
"Everywhere in your travels, you do see the fairly big limbs down," says Smeaton. "When you're on the interstate, you'll see tree limbs on the shoulder. It definitely hit a wide area; it didn't go through a distinct row."
Although people are anxious in the wake of the storm, says Smeaton, a crisis like this brings communities together in a way almost nothing else can. He says the workers from Ontario, who volunteered to help out on a holiday weekend, are being treated "like a breath of fresh air."
They're not getting much fresh air in return, though. Crews are working 16-hour days in sweltering 38C heat.
Hydro Quebec has about 70 workers assisting local crews in Maryland. They will stay until restoration is complete or local crews can handle the work on their own.
U.S. officials said power was back for more than a million customers but lights — and air-conditioning — were still out for about 1.4 million homes and businesses.
Hydro One and Hydro Quebec have agreements with North American utilities to help out during significant power outages. When Canadian workers are sent to the U.S., they are paid by the U.S. utility companies.
New Brunswick's utility, N.B. Power, has a similar deal but did not immediately send relief, though it may be asked to do so later.
In February 2010, Hydro One assisted utilities in Vermont in after a winter storm. In September 2008, its crews travelled to Ohio to help restore power after hurricane Ike caused major outages.
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