Storm Nicholas made landfall in Texas, bringing torrential rainfall that threatens to unleash flooding in Houston and parts of Louisiana still recovering from Hurricane Ida two weeks ago.

Nicholas, downgraded to a tropical storm after briefly being rated a hurricane, roared ashore at about 12:30 a.m. local time near the Matagorda Peninsula. It has top winds of 70 miles per hour, the National Hurricane Center said in its latest advisory. It's the eighth tropical cyclone to hit the U.S. this year.

There were more than 420,000 customers without power in the Houston area, Centerpoint Energy Inc. reported.

While Nicholas will mostly bypass the Gulf of Mexico's oil and natural gas platforms, it could dump as much as 18 inches of rain, posing a threat to coastal refineries and petrochemical facilities. The region's energy sector is still recovering from the impact of Hurricane Ida more than two weeks ago, with about 44 percent of the Gulf's offshore crude capacity offline. Oil futures traded higher Tuesday on speculation Nicholas could add to the disruption to supply.

Louisiana Gov. John Bel Edwards declared a state of emergency and Texas Gov. Greg Abbott ordered emergency crews to get ready for the storm. A hurricane warning stretches from Port O'Connor to Freeport, Texas, and the heaviest rain will likely fall from Monday to Wednesday, according to the Weather Prediction Center. The storm surge could reach five feet at Galveston Bay in Houston.

"Houston is in the crosshairs," said Steve Silver, a senior meteorologist with Maxar, noting that precipitation poses a bigger threat than wind. Nicholas will be "a significant rainfall event."

The storm's slow forward advance adds to the flooding risk as it passes over the region.

Nicholas is the Atlantic's 14th storm in 2021. Half of the storms so far have hit the U.S., and Ida was the season's worst, crashing into the Louisiana coastline before devastating New York with rain and floods that killed more than 40 people. On Monday, AIR Worldwide updated its projected losses from Ida, saying the storm probably caused $20 billion to $30 billion in insured losses. Earlier estimates were around $18 billion.

The latest storm is expected to hit areas of Louisiana still recovering from last year's Hurricane Laura and is likely to bring heavy rain to areas slammed by Ida, Edwards said. That could also disrupt efforts to restore power.

Nicholas may also disrupt restoration efforts of Gulf of Mexico oil platforms and pipelines that have remained offline since Ida. Nearly 50 percent of oil supply is still down in the Gulf and the volume of shut-in output may start growing once again. U.S. Gulf Coast physical crude prices could surge if supplies aren't returned promptly.

An average Atlantic season produces 14 storms by the time it ends in November, so 2021 is ahead of pace.