Updated

It could take days to restore power to hundreds of thousands of people around Washington after a storm downed power lines and trees and left four people dead, officials said Monday.

The Sunday storm brought cooler weather to the Mid-Atlantic region, which has been through a nearly two-week heat wave, but also left widespread damage in Washington and its suburbs.

Power outages affected more than 430,000 customers. Officials said they hadn't seen a similar outage since Hurricane Isabel in 2003.

Regional utility Pepco reported late Monday that more than 203,000 customers were without power in Washington and neighboring Maryland counties. The widespread damage made it unclear when most would be restored, spokesman Bob Hainey said. Major power lines were down, electric poles were broken, and numerous transformers were damaged.

Other electric companies in the region predicted power would be mostly restored by Monday or Tuesday night.

Four deaths in the region were blamed on the storm.

Officials say 63-year-old Warren Douglas Smith died after encountering severe winds and choppy seas on the Chesapeake Bay while trying to return to land on personal watercraft.

In Beltsville, Md., a tree crushed a minivan, killing 44-year-old driver Michelle Humanick and injuring her passenger.

In Virginia, a 6-year-old boy also died after a tree fell on him while he was walking with his family. In Pennsylvania, police say a 53-year-old woman was apparently electrocuted by a fallen power line in her back yard.

Even as cleanup was going on, the power outages were causing disruptions. Numerous traffic signals were out. In Fairfax County, firefighters responded to 22 fires in the storm's aftermath, and nine car accidents were blamed on the storm. In Prince George's County, Md., darkened traffic signals caused about a dozen accidents.

In Washington, officials said there were more than 270 reports of damage from fallen trees or limbs. Fire department spokesman Pete Piringer said about half a dozen homes were significantly damaged by falling limbs. Three cars caught fire as a result of downed power lines.

Mike Allen, 22, was in the attic of his mother's home in Washington when he heard a loud boom. A three-story tall tree had fallen, uprooting a power pole, blocking the home's front entrance and cracking an attic wall.

"There are a lot of streets in the neighborhood where a similar thing has happened," he said. "It's pretty wacky."

Bethesda, Md., resident Mei Zhang initially enjoyed looking at the storm before her power went out.

"The storm hit. The trees were swirling. It was an incredible show outside my window ... It reminded me of 'Wizard of Oz,'" she said.

Officials warned residents of downed lines. Baltimore Gas & Electric said about 18,000 customers were without service late Monday, down from 112,000. The majority were expected to have power by Tuesday evening. Dominion Virginia Power reported 3,300 customers without power, down from 94,000. Most of those should have power Monday night.

The Washington Suburban Sanitary Commission said the storm also cut off power at its filtration plant that provides water for nearly 2 million people in suburban Maryland. Mandatory restrictions on water use were lifted late Monday after power was restored.

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Associated Press writers Nafeesa Syeed, Matthew Barakat and Lauren Sausser contributed to this report.