The rain-saturated ground "makes it easier for flash flooding" to occur, said National Weather Service meteorologist Ian Morrison. "There are a lot of heavy showers out there right now."
On Tuesday night, emergency shelters were opened for residents in areas experiencing flooding. About 15 people spent the night at a shelter at Hana High School, while eight people slept overnight at the War Memorial Gymnasium.
Lisa Higa's two children and mother had to be rescued from the roof of their Iao Valley home when water started pouring into their house.
"My son, who is 11 years old, he put on a life vest and he put a life vest on my daughter. He put a life vest on my 74-year-old mom and they went to the roof and they waited there," she explained.
Higa and her family were almost done renovating their home, but now every room is ruined.
"Our property is about 2.5 acres and we're on the very opposite side of the river, so you would never think that we would get hit with something like that. We're so far away," Higa said.
The raging Wailuku River also swept a backhoe downstream.
"It was parked kind of alongside the bank. The bank was a lot higher than the river at the time," said Kaleo Ornellas, the son of the farmer who owns the backhoe.
Also Tuesday, firefighters responded to several reports of vehicles being caught in flood waters. In one case, a motorcycle was swept into rushing waters, but the motorcyclist was able to escape unharmed. Near Olowalu Stream, meanwhile, flood waters trapped a woman in her vehicle until good Samaritans arrived to pull her to safety.
Iao Stream's raging waters also caused a partial collapse of the parking lot at Kepaniwai Park, and several mudslides inundated the area with debris, Maui County officials said. The park is closed until further notice.
"It was pretty incredible. For 35 years I've been here, and it's the first time that I've heard the river with so much fury," said Iao Valley resident Charlie Pico.
Meanwhile, crews are working to clear debris from roadways.
The Manawainui Bridge has been closed due to a rockslide, while flood closed Piilani Highway near mile marker 30.
Crews were also working to clear debris from landslides on Hana Highway near mile markers 14 to 16. Honoapiilani Highway was also closed in several areas due to Ukumehame River overflowing and landslides near mile marker 1 and mile marker 7.
On Maui’s west side, a flash flood came dangerously close to homes in Kauaula Valley, which is above Lahaina.
“Heavy downpours and constant rain and a lot of water just flowing everywhere,” said Lahaina resident Mark Palakiko. “And because we live in the valley, there's water just piling up everywhere. And then of course the river, the river just gets too crazy, where we can't even get out of the valley."
Palakiko said the raging river came up to a 10-foot wall.
"What you see is actually about four feet of water covering over our driveway which already is about maybe five to six feet above the bottom of the riverbed. So the amount of water you see coming over is tremendous," he said.
The heavy rains also flooded the streets of Lahaina town and prompted an islandwide brown water advisory.
Other problems reported include:
A water line serving Iao Valley was washed away, interrupting water service to residents.
Several homes were flooded in Pukalani, though the extent of the damage is unknown.
Baldwin Park, Papalaua Wayside Park and Iao State Park are closed, pending area assessments.
The Mala Ramp in Lahaina is closed because of debris from Kahoma Stream runoff.
Meanwhile, Central and South Maui residents are being urged to boil their water for three minutes before consuming due to possible contamination from flooding. Also, residents in Wailuku, Kahului and Lahaina area being told to conserve water. Lahaina is an area of particular concern because the Lahaina Water Treatment Plan is not operating due to the heavy rains.