The National Hurricane Center has downgraded Harvey from a Category 1 hurricane to a tropical storm.

But officials say they are still worried about potentially catastrophic rainfall that will continue for days, with more than 40 inches and flash flooding possible even well inland.

Harvey came ashore Friday along the Texas Gulf Coast as a Category 4 storm with 130 mph winds, the most powerful hurricane to hit the U.S. in more than a decade.

Experts say hurricanes almost always lose strength quickly after making landfall and moving away from the warm waters that fuel their winds. But the danger doesn’t end there.

Harvey is expected to keep slowing and dumping rain through the middle of next week.