Update (5:34 p.m.): Just announced: The lobby of the county administration building at 2100 Clarendon Blvd. in Courthouse will be open as a cooling center until 9 p.m.

Update (5:08 p.m.): Patch reported this morning that 911 service was sporadic in the wake of Friday night's storm. Arlington County acknowledged that was the case about an hour ago and recommended residents call or go to their nearest fire station to report an emergency if they can't reach the emergency communications center.

The county, too, has started a list of weather-related cancellations and delays.

So far, three cooling-off centers — Artisphere, Walter Reed Community Center and Central Library — have been listed as being open Sunday.

At about 4:30 p.m., the county released a statement saying that nearly 300 people had already sought shelter in cooling centers Saturday.

"It will take several days for life to get back to normal. We urge people to stay out of the heat, stay hydrated, drive safely and check on their neighbors," Arlington County Manager Barbara Donnellan said in a statement.

Original post (2:09 p.m.): Arlington County slowly began returning to normal Saturday after a fast-moving, severe thunderstorm slammed the region Friday night and left more than 1 million people without power in the greater Washington area, downed trees and killed at least two people in nearby Fairfax County.

"It's pretty extensive," Arlington County Emergency Management Director Jack Brown told Patch at about 1 a.m. Saturday, as crews began what likely will be a long cleanup process.

More than 59,000 households in Arlington woke without power, which accounts for about 60 percent of the county. By 1:30 p.m., that number was down to about 50,000. Dominion Power has said it could be several days before electricity is fully restored.

Metro closed Courthouse Station due to a power outage and is providing bus service between Rosslyn and Clarendon. Lunch spots around Courthouse plaza were packed full around noon as people tried to squeeze in to feel the air-conditioning or try to snag a WiFi signal. AT&T and Verizon have reported cellular and Internet connectivity problems in the wake of Friday's storm, which is known as a derecho.

Traffic signals at about 80 Arlington County intersections are without power. While police are bringing in extra officers to assist with traffic control, motorists are reminded to treat each blacked-out intersection as if it was a four-way stop.

Temperatures today are expected to reach 100 degrees again — with a heat index of 110. The county government has released the following list of air-conditioned buildings that are open to anyone who needs to cool down:

• Artisphere, 1101 Wilson Blvd. (open until 11 p.m.)
• Walter Reed Community Center, 2909 16th St. S. (open until 9 p.m.)
• Madison Community Center, 3829 N. Stafford St. (open until 6 p.m.)
• Department of Parks and Recreation Trades Center, South Taylor Street, just off South Arlington Mill Drive in Shirlington
• Pentagon City Mall, 1250 S. Hayes St.
• Aurora Hills Library, 735 S. 18th St. (open until 6 p.m.)
• Central Library, 1015 N. Quincy St. (open until 6 p.m.)

All of Arlington County's pools have been closed.

The county's water system has not been compromised, but officials have asked residents to conserve when they can.

Gov. Bob McDonnell declared a state of emergency in Virginia at about 12:30 p.m. Arlington County Manager Barbara Donnellan declared a local emergency shortly thereafter.

Report power outages to Dominion at 866-366-4357.

Report down trees to Arlington County at 703-228-6525.

For more cleanup and emergency contact information, check the county's "After the Storm" page.