Tropical storm Nicholas hit Texas and parts of Louisiana with heavy rain, power outages and the threat of flash floods as well as storm surges Tuesday morning as it moved inland from the Gulf Coast, according to NBC News.

Nicholas strengthened to a Category 1 hurricane before making landfall overnight on the eastern part of Texas’ Matagorda Peninsula with 75 mph winds and the prospect of up to 18 inches of rain, according to the National Hurricane Center.

It was downgraded to a tropical storm at 5 a.m. ET Tuesday but still had the power to cause “life-threatening flash floods in the deep south in the next couple of days,” the hurricane center said. The storm, which had maximum sustained winds of 60 mph, was about 15 miles south-southwest of Houston and about 90 miles west-southwest of Beaumont, Texas, according to an 8 a.m. ET update.

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Harris County, which includes Houston and is one of the most populous counties in the country, was bracing for severe rainfall and disruption, with warnings of possible flooding in the county’s southeast.

The same flash flood warning covered parts of Brazoria County, Chambers County and Galveston County, where heavy rainfall continued to fall overnight.

A storm surge warning was also issued by the National Weather Service early Tuesday along the Texas coastline from Sargent to Sabine Pass, including Galveston Bay.

More than 470,000 customers were without power in Texas in addition to 95,000 in Louisiana, just after 8 a.m. ET, according to poweroutage.us.