Hawaii braced for widespread flooding early Saturday as Hurricane Lane, downgraded a day earlier to a tropical storm as its winds weakened, brought heavy rain to the area.

The National Weather Service warned of more “life-threatening” flash flooding in the archipelago, where the storm had already brought landslides, floods and power failures. Some areas had already seen more than three feet of rain because of the storm. The National Guard was deployed to help with search-and-rescue efforts.

Three fires had broken out in West Maui, possibly caused by downed power lines and most likely stoked by the whipping winds, said Alan Arakawa, the mayor of Maui. By Friday afternoon, two fires were completely contained but still burning, and the third, affecting about 1,500 acres, was about 40 percent contained.

“We were expecting flooding, high winds, big surf — we weren’t expecting very little rain, heavy winds and a big fire,” Mr. Arakawa said. “We’re hoping for just enough rain to put out the fires, not enough rain to have mudslides after that.”