(Bloomberg) -- High winds and heavy rains tore through storm-battered Texas Tuesday, grounding flights, flooding streets and leaving more than 1 million homes and businesses without power — some possibly for days.  

The storms, striking less than a week after deadly tornadoes ripped across North Texas, lashed the Dallas and Houston areas with winds that uprooted trees and toppled power lines. Traffic on highways slowed to a crawl, cars and trucks pulling onto shoulders to avoid wind-blown debris. As hail pounded rooftops, tornado sirens sounded across the region, with radio and TV stations urging residents to seek shelter. 

The damage to the electric grid was so extreme that some equipment will need to be rebuilt rather than repaired, a spokesman of utility Oncor Electric Delivery Co. said. 

“These storms produced baseball-sized hail, winds in excess of 80 miles per hour and a significant amount of cloud-to-ground lightning,” Oncor’s Grant Cruise said at a press conference. Some outages, he warned, would likely last for days.

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The storms arrived as Houston, the nation’s fourth-largest city, is still recovering from a May 16 windstorm that tore windows from downtown office towers and smashed them on the pavement below. Tuesday’s storms battered the same damaged skyscrapers, with more reports of falling glass downtown, Houston Office of Emergency Management representative Brent Taylor said in an interview.

Tuesday’s rough weather led to 523 delayed flights and 59 cancellations at the city’s George Bush Intercontinental Airport, according to aviation tracker FlightAware LLC. Dallas Fort Worth International Airport, a hub for American Airlines Inc., fared worse, with 866 delays and 450 cancellations.

“The winds were very strong, it got dark, the rain was coming down very hard,” Mary Benton, a representative for Houston Mayor John Whitmire, said by phone. “It hit Houston pretty quickly.” 

Several Dallas-area nursing homes were running on backup generators, said Dallas County Judge Clay Lewis Jenkins.

Heavy rains will likely drench the Dallas-Fort Worth area overnight, with the potential for another 1 to 3 inches falling, said forecaster Bryan Jackson with the US Weather Prediction Center. Wednesday may see a lull, with localized severe storms popping up, but Thursday looks like another wild day throughout the southern Plains and Texas, he said.

“It is a real active pattern,” Jackson said.

In addition to the storms, high temperatures and humidity will bear down across southern Texas, pushing heat index values as high as 110F (43C).

Unsettled spring weather has produced strong storms across the central US, from the Plains and Midwest to the South. Warm, moist air flowing north from the Gulf of Mexico is colliding with cool, drier air moving south from Canada as well as storms crossing the Rocky Mountains. April produced 384 tornado reports around the US, the second highest count on record, according to the US National Centers for Environmental Information. 

Tuesday’s intense weather followed a weekend of heavy tornado activity in Texas. On Sunday, at least 17 people died after twisters struck parts of Texas, Oklahoma and Arkansas. Half the fatalities occurred after one of the tornadoes tore through North Texas. 

A large area in the Texas Panhandle, including Lubbock, was under a tornado watch Tuesday, meaning the deadly storms could occur, the National Weather Service said.

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