A severe storm in Houston, the fourth-largest city in the US, has killed at least four people and left over 800,000 homes and businesses without power.

The Houston school district closed all public schools on Friday and said they would reopen on Monday.

Flights were grounded at the city's two major airports because of the weather. Sustained winds topping 60 mph were recorded at Bush Intercontinental Airport.

At least four people were killed due to the storm, Houston Mayor John Whitmire told reporters in a news briefing on Thursday night, "We have a storm with 100 mph winds, the equivalent of Hurricane Ike, considerable damage downtown." Whitmire said that the region may have been hit by tornadoes as well and urged people to "stay at home".

"There's trees across roadways across Houston," he said, adding, "I ask everyone to be patient, look out for your neighbours. It will take 24 hours for a lot of this power to be restored, some will require 48 hours." Houston Fire Chief Samuel Pena told reporters that of the four fatalities, at least two were caused by fallen trees, while another due to a “crane that was blown over by the wind".

The wind estimated to be in excess of 70 mph toppled trees, blew out windows of high-rise buildings and caused transmission towers holding power lines to crumble. The Harris County Sheriff’s Office encouraged everyone to stay off the roads as trees blocked streets, with power outages climbing above 800,000 in the Houston metro.

The local National Weather Service office issued several Tornado Warnings for the Houston metro but by the time the storms cleared, it was strong winds that are believed to have caused most of the damage.

The broken glass and debris forced city leaders to encourage workers to stay home on Friday and avoid the downtown region.

Several downtown office buildings lost windows. Flash flood and severe thunderstorm warnings were issued for multiple counties heading into the evening, according to Houston's National Weather Service office.

"Take shelter now if you're in the path of this storm. Head to the lowest floor!" the NWS office earlier warned on social media.

Streets were flooded, cars were stuck on the flooded roads and trees were down across the region. Majority were heading home after days’ work, but the sudden terrible rain made them stop and take shelter in nearby restaurants or malls.

"Please avoid the roadways if possible, but if you're out, please use caution and be on the lookout for debris," Harris County Sheriff Ed Gonzalez wrote on social media. Gonzalez shared an image of vehicles attempting to traverse around a massive tree that had come crashing down into an intersection.

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