Harvey weakens to a tropical depression

Harvey, previously a tropical storm, has weakened into a depression, the US National Hurricane Center says.

Harvey is now about 15 kilometres southwest of Alexandria, Louisiana, with maximum sustained winds of 55 kilometres per hour, the Miami-based weather forecaster said.

Catastrophic and life-threatening flooding continues in southeastern Texas and portions of southwestern Louisiana, the NHC said, adding that the threat of heavy rains has ended in the Houston/Galveston area.

"However, catastrophic and life threatening flooding will continue in and around Houston, Beaumont/Port Arthur, eastward into southwest Louisiana for the rest of the week," the NHC said.