Houston Fire Chief Samuel Peña said official causes of death have not been determined, but officials estimate two people died from downed trees and one person died from an overturned crane.
The school district canceled classes on Friday and Houston Mayor John Whitmire urged non-essential employees to stay away from work and roads as glass scattered across downtown, traffic lights went out all over the city and trees and power lines blocked streets and highways.
The storms primarily affected northwest Houston, Houston Heights, the central business district and east Houston.
All municipal departments were working through the night Thursday to clear debris and open centers for people in need of medical attention, homeless or without power.
About 900,000 customers statewide were without power early Friday morning, according to Poweroutage.us, most of them in Harris County, where Houston is located. Whitmire said it could take 24 to 48 hours to restore power.
He added that the city had not heard from anyone stranded, but there was a backlog of 911 calls. Peña said most of them were related to a gas leak. The state has sent Department of Public Safety officers to evacuate the downtown area so Houston police can focus on monitoring the calls.
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According to the National Weather Service, heavy rainfall is expected in the region on Friday and flash flooding is possible.
"But the real emphasis tonight is to stay home," Whitmire said. "Do not travel on the roads. It's dark out. There are trees across the roads in Houston, so be very patient, be careful, watch out for each other."
"Take care of your neighbors, your family, your pets and let's move on," he added.
