The most powerful hurricane to hit the U.S. state of Texas in more than 50 years moved slowly inland on Saturday, dumping torrential rain expected to cause catastrophic flooding after battering the coast with 130 mph winds.

According to the National Hurricane Center, Hurricane Harvey had weakened to a Category 1 and was likely to become a tropical storm later Saturday.

Texas utility companies said nearly a quarter of a million customers were without power. Residents and emergency respondents were still sheltering from the storm early on Saturday, making it difficult to gauge the full extent of the damage.