(CNN) — Storms battered Texas and Louisiana late Thursday and early Friday with destructive winds and torrential rain, leaving at least four dead, flooded roads and more than 1 million homes and businesses without power — and more floods could plague parts of the Gulf Coast Friday.

At least four people died as the severe weather blasted through Houston, the mayor’s chief of communications Mary Benton told CNN. Fallen trees appear to have caused two of the deaths, and a crane accident caused another, Houston Fire Department Chief Samuel Peña said in a press conference Thursday night.

Violent weather left a trail of damage to buildings in Houston, blocked roadways with fallen trees and debris and mangled power lines, leaving numerous residents in the dark. More than 892,000 homes and businesses were without power across Texas and more than 211,000 in Louisiana as of early Friday, according to PowerOutage.us.

The storm was so powerful that it blew out the windows of buildings in downtown Houston, littering the area with glass as traffic lights went dark. Shoppers at a Costco in Houston used their phones as the only source of light as they huddled in the dark inside the store when the power went out, with employees closing the doors to block out the rain and winds.

Soaking storms will shift east on Friday and target more of the Gulf Coast after rumbling to life Thursday afternoon in parts of Texas. The large cluster of thunderstorms brought with it a flash flood threat from the heavy downpours and severe storm dangers in the strongest cells.

More than 30 million people are at risk of severe weather Friday across parts of the Gulf Coast, with 1 million people under a Level 3 of 4 moderate risk of excessive rainfall.

Significant swaths of Mississippi and Alabama are under the moderate risk of excessive rainfall on Friday. A larger area from the Texas-Louisiana state line to Georgia and the Florida Panhandle is under a Level 2 of 4 risk.

Drenching storms will likely last into Friday morning for parts of the Gulf Coast. An initial round of flash flooding is likely in the first half of Friday before rain starts to taper off in the afternoon.

Another bout of heavy rain will develop Friday night and continue into the earliest hours of Saturday morning, working over the same areas hit earlier in the day. These storms could produce rainfall rates of 2 to 3 inches per hour, and quickly restart or worsen any ongoing flooding.

Widespread rainfall totals of 2 to 6 inches are expected from Texas to Georgia through Saturday morning. A few spots caught under multiple torrential storms may pick up 8 inches or more of rain. Some areas could record close to a foot of rain in about 48 hours.

Here’s the latest on ongoing storms in the southern US:

Twisters could swirl through some areas: A tornado watch is in effect until 3 a.m. CT Friday for parts of southeast Louisiana. The watch covers over 2.5 million people and includes the cities of Baton Rouge and New Orleans.

Excessive rainfall and severe thunderstorms threaten South again: “Heavy to excessive rainfall is forecast for eastern Louisiana into central Alabama which could bring flash, urban, and riverine flooding Friday,” the National Weather Service said. “Scattered severe thunderstorms with a few tornadoes, very large hail, and damaging winds are possible across parts of the Gulf Coast States Friday and Friday night.”

Most of Houston’s traffic lights are down: Traffic lights across the city are down and debris from damaged buildings and toppled trees are covering roadways, making driving conditions dangerous. “Downtown is a mess. It’s dangerous due to the glass and the lack of traffic lights. So stay at home,” Houston Mayor John Whitmire said Thursday.

Major flooding leads to water rescues: With major flooding hitting Bryan, Texas, on Thursday, police spokesperson Seth Waller said there have been up to 20 water rescues after residents drove into the water. Nearby, in College Station, videos shared with CNN on Thursday showed heavy rain flooding a park in the area.

Floods deluge roads: Several roads closing in northern and eastern Bosque County, Texas due to water over crossings or bridges. There have also been several flooded roads throughout Bell County. McLennan and Falls counties also reported roadway flooding.

Hurricane-force wind gusts reported in Texas and Louisiana: The National Weather Service in New Orleans reported strong winds as high as 84 mph. Wind gusts measuring 78 mph were also recorded near San Jacinto River at I-10 and 74 mph in Channelview, Harris County, on Thursday evening, according to the National Weather Service.

Houston area bears brunt of destructive storms

Violent storm conditions in Houston have blown out skyscraper windows, partially collapsed a nightclub and partially ripped roofing off the downtown Hyatt Regency, showering the hotel lobby with rain and debris, according to witness video. CenterPoint Energy says its skyscraper in downtown Houston has sustained damage of the storm, according to a spokesperson.

Multiple steel power transmission towers in Houston were also mangled by the storms, CNN affiliate KPRC reported. Along part of US Route 290, traffic was stopped as firefighters cleared downed lines draped over the roadway.

The weather service had issued a severe thunderstorm warning with the highest-level “destructive” tag for Houston, urging residents to take cover immediately in a post on X. There were reports of winds up to 78 mph on the east side of the city.

Houston Mayor John Whitmire advised residents to stay off the roads and stay at home. Most of the traffic lights across the city are down and it could take anywhere from 24 to 48 hours for power to be restored.

“The mayor and first responders are asking Houstonians to stay off the roads and avoid all unnecessary travel. Many roads are impassable due to downed power lines, debris, and fallen trees,” the mayor’s office said in a statement Thursday evening.

The Houston Independent School District has announced campuses will be closed on Friday and will reopen next week. “Due to widespread damage across Houston, HISD has coordinated with the City of Houston and is closing all campuses on Friday, May 17. Schools will reopen on Monday, May 20,” the school district said in a message on Facebook.

More than a dozen Houston-area school districts announced they would close Friday as well, including Aldine Independent School District, Channelview Independent School District and Cypress-Fairbanks Independent School District.

Texas has been in the bull’s-eye of seemingly unrelenting rounds of flooding downpours. On Wednesday, Gov. Greg Abbott requested a presidential disaster declaration for areas of the state impacted by the recent onslaught of severe weather and flooding. He said there has been “extensive damage caused by these severe storms, historic river flooding, and tornadoes” that began on April 26.

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