Tropical Storm Beryl’s howling winds and torrential rain killed at least two people, closed oil ports, grounded hundreds of flights and knocked out power to more than 2 million homes and businesses in southeast Texas on Monday.

Beryl, the season’s earliest Category 5 hurricane on record, weakened from a hurricane after pounding the coastal Texas town of Matagorda with dangerous storm surges and heavy rain before moving across Houston, the US National Hurricane Center (NHC) said.

The storm, which was expected to rapidly weaken as it moved inland, swept a destructive path through Jamaica, Grenada, and St. Vincent and the Grenadines last week. It has killed at least 12 people in the Caribbean and Texas.

In Texas, a 53-year-old man and a 74-year-old woman were killed in two incidents by trees that fell on their homes in the Houston area on Monday, according to Harris County officials.

The state’s energy industry, the nation’s biggest producer of US oil and natural gas, braced for Beryl’s impact as the powerful storm slowed refining activity and prompted the evacuation of some production sites.

“Life-threatening storm surge and heavy rainfall is ongoing across portions of Texas. Damaging winds ongoing along the coast, with strong winds moving inland,” the NHC said even as Beryl began to lose strength.

Following warnings that it could be a deadly storm for communities in its path, residents had rushed to board up windows and stock up on fuel and other essential supplies.

Before daybreak, strong gusts and torrential rain lashed cities and towns such as Galveston, Sargent, Lake Jackson and Freeport, television footage showed. By late morning, many fallen trees blocked roads in Houston as the worst of the storm passed, with persisting winds and some road flooding, rendering lanes on major freeways impassable. The city barricaded flooded areas.

In video posted on social media by Houston’s local ABC station, crews using a life jacket and ladder fire truck rescued a man from a truck on a flooded stretch of freeway.

In a late morning press conference, Houston Mayor John Whitmire urged people to shelter in place. He noted that flood waters exceeded 10 inches (25 cm) across most of the city.

“We’re literally getting calls across Houston right now asking for first responders to come rescue individuals in desperate life safety conditions,” Whitmire said.

The storm had strengthened into a Category 1 hurricane as it crossed the warm waters of the Gulf of Mexico before making landfall. But the NHC said it was now expected to weaken rapidly as it moves across land, as hurricanes typically do, before becoming a tropical depression on Tuesday.

Beryl was expected to barrel over eastern parts of the state through the day before moving into the Lower Mississippi Valley and the Ohio Valley on Tuesday and Wednesday, the NHC said.

“People in the path of Beryl’s track should not let their guard down this week,” Accuweather said in a statement, warning of possible tornadoes as far away as Ohio and possible flash flooding as far north as Detroit.

President Joe Biden is being regularly updated about the storm while administration officials remain in close contact with state and local counterparts, a White House official said.

The Federal Emergency Management Agency (FEMA) and the US Coast Guard had prepositioned staff to assist with search and rescue efforts, with FEMA also readied with water, meals and generators to boost local response efforts, according to the Biden administration.

Schools said they would close as the storm approached. Airlines canceled more than 1,300 flights, and officials ordered a smattering of evacuations in beach towns. Small businesses in Houston, including package delivery services and chiropractors, delayed openings or were closed on Monday.

More than 2 million homes and businesses in Texas have lost power, according to local utilities and PowerOutage.us data.

Several counties in southeastern Texas — including Houston, where many US energy companies are headquartered — are under a flash-flood warning as thunderstorms unleashed up to nearly 12 inches (30 cm) of rain in some areas.

Resident Gary Short said he was most concerned about possible flooding, which the NHC warned was expected across parts of Texas into Monday night.

“I’m more worried about the rain than anything,” he said as he filled up cans with gasoline at a service station on Sunday. “Other than that, not too concerned. Just getting ready.”

Closures of major oil-shipping ports around Corpus Christi, Galveston and Houston ahead of the storm could disrupt crude oil exports, along with shipments of crude to refineries and motor fuel from the plants.

Some oil producers, including Shell and Chevron evacuated personnel from their Gulf of Mexico offshore production platforms ahead of the storm.

Marathon Petroleum Corp’s refinery in Texas City, Texas was hit by a power interruption on Monday amid the storm, the company said in a statement.