Swollen streams were filled with logs and branches, and roads flooded from rain that fell at a rate of 3 to 4 inches an hour this morning.

The National Weather Service this morning placed Kaua'i under a flash-flood warning that was expected to last until 12:30 p.m. Kaua'i and O'ahu were under a flash flood watch until 4 p.m. today.

Kaua'i police reported that the Hanalei Bridge was closed at mid-morning because of flooding on Kuhio Highway. And on the south side of the island, in Kalaheo, water flowed over Waha Road near Lauoho Road.

Although the rain was tapering off, runoff continued to cause flooding in the area.

"O'ahu is clearing gradually, but Kaua'i is going to be in the thick of things for awhile," said weather service forecaster Brad Fujii. "The system will be tapering off by tonight."

Overnight rain was heaviest in 'Oma'o, where 3.26 inches fell from 2 a.m. to 8 a.m., Fujii said. In Lihu'e, 1.96 inches fell during the same period, he said.

On O'ahu yesterday, heavy afternoon rain trapped three people in their cars, including a couple in their 70s, after they stalled in fast-moving flood waters on Kamehameha Highway in Waikane. Firefighters rescued the motorists.

The flooding was the result of a downpour over parts of Windward O'ahu that closed the highway for more than two hours and prompted the closing today of Kahuku High & Intermediate School.

Three cars stalled on a small bridge between Waiahole and Waikane valleys about 8 p.m. and were in danger of being swept off the road by the thigh-high torrent.

Fire Battalion Chief Hiram Keliipio estimated that at its peak, the flood water was about three feet high and moving at more than 20 mph.

"The water there was halfway up to the hood," Keliipio said of the elderly couple's car. "It was moving."

One man managed to walk to safety, but a man in a small pickup truck and the elderly couple in a sedan could not get out of their vehicles.

Keliipio said fire rescue personnel felt the safest thing to do was to wait for the rain to subside, allowing the water to recede.

"We had difficulty walking up to that car. When we got there, we felt the best thing to do was to leave them in place. We strung a safety line across the road in case any of us fell down.

"If you fell in the water, and came down the road, you had a 50-50 chance of coming over the bridge or getting sucked under the bridge, and if you went under the bridge, you were gone."

When the water level dropped to about a foot, firefighters placed harnesses around the motorists, tethered them to rescue workers and walked to safety.

Keliipio said the couple was smart to stay in their car and not attempt to battle the current. But, he said, had the rain continued, they were in danger of washing away.

The bridge closure shut down Kamehameha Highway from about 7:40 p.m. to shortly before 10.

Waikane resident Lydia Garcia, who has lived along Kamehameha Highway next to the bridge for more than 20 years, said it hadn't been raining that hard, and she was surprised the road flooded. She said the problem is that a lot of silt under the bridge needs to be cleared.

Parts of O'ahu were battered by thunderstorms for a third straight day. Kahuku got 4.24 inches of rain in the 12 hours ending at 8 p.m., while Punalu'u got 2.35 inches in that same period.