Emergency crews raced to pull people from cars and homes as flood waters rose across southeast Texas on Sunday, rescuing more than 1,000 people around Houston as Tropical Storm Harvey pounded the region.

Harvey came ashore late Friday as the most powerful hurricane to hit Texas in more than 50 years and has killed at least two people. The death toll is expected to rise as the storm lashes the U.S. state for days, triggering more floods, tidal surges and tornadoes.

Harvey has caused chest-deep flooding on some streets in Houston as rivers and channels overflow their banks. After up to 30 inches (76 cms) of rain in some parts of the fourth most-populous U.S. city, the storm is expected to dump 12 to 25 more inches (30-63 cms) over the next few days, the National Weather Service forecast. The total could reach 50 inches in some coastal areas of Texas by the end of the week, or the average rainfall for an entire year.

“This event is unprecedented and all impacts are unknown and beyond anything experienced,” the government’s National Weather Service said on Twitter.

The center of Harvey is still 125 miles away from Houston, and forecast to arc slowly toward the city through Wednesday.

Flooding closed many roads and residents hunkered down inside houses and apartments as authorities sent flash flood and tornado alerts to cell phones.

The swift rise of flood waters surprised authorities and residents with boats were asked to help with rescues.

The Ben Taub Hospital in Houston’s Medical Center was being evacuated on Sunday. An American Red Cross emergency shelter was forced to shut due to flooding and the group opened two more, including one in a convention center in downtown Houston.

“Within less than a half hour, we had 7 to 8 inches of water in our first floor,” said Brian Hoskins, 25, a petroleum engineer who lives in Houston.

“I was worried about losing all our furniture and our cars.”

Emergency services told people to climb onto the roofs of their houses rather than into their attics to escape rapidly rising waters, to avoid being trapped if waters rose more.

Authorities warned the city’s more than two million residents and people across Texas not to leave homes even if they flooded because roads were impassable.

Many people were stuck in vehicles on raised highway sections with dips in the roads ahead of them flooded.