The National Weather Service continued a flash-flood warning for O'ahu through about 1 this afternoon but canceled a flash-flood watch for the Big Island and Maui. Kaua'i and Moloka'i remained under a flash-flood watch until 4 p.m., however.

A pickup plows through ponding water at Hobron Lane and Ala Moana. Jeff Widener • The Honolulu Advertiser

Even though Darby had lost much of its oomph by the time it reached the Islands yesterday, it combined with atmospheric conditions that were perfect for heavy rain, according to Derek Wroe, a meteorologist with the weather service.

It drifted over the Big Island yesterday, closing schools and roads, then arrived in the middle of the night on O'ahu.

Hawai'i Kai was hit hardest today with 3.3 inches of rain falling between 2:45 a.m. and 5:45 a.m., Wroe said.

"The system is moving west slowly," Wroe said. "We are expecting it to lift and clear out of O'ahu by the afternoon. And that would put Kaua'i next in line for the heavy rainfall."

The Hawaii State Farm Fair canceled its Thursday program because of heavy rains in Kapolei, organizers said. "We are on standby for Friday and we'll be watching weather conditions like the rest of O'ahu," Donna Smith of E.K. Fernandez Shows said.

Darby's brief stay created a soggy mess all over the map.

Police closed Kalaniana'ole Highway in both directions at Makapu'u Lookout because of a landslide just before 3 a.m., and re-opened the road at 8 a.m. Kamehameha Highway was closed intermittently overnight at Waiahole Valley Road because of flooding. By 8:15 a.m., one lane had been opened, police said.

Scott Ishikawa, state Department of Transportation spokesman, said about a dozen large rocks came down the hillside in two nearby spots in the area, the largest of which was about three feet in diameter. Most were penned behind the netting installed along the overhang, but some fell onto the roadway, Ishikawa said.

In addition to the highway flooding near Waiahole, he said, water was ponding in a section of the H-1 Freeway viaduct near the Ka'onohi Street overpass. The ridership requirements of the carpool and Zipper lanes were waived at about 6 a.m. to allow more people to use available lanes into town, and the Zipper lane hours were extended until 9:30 a.m. to accommodate more town-bound traffic.

Shortly after 9 a.m., an accident in the Kane'ohe-bound lanes of the Likelike Highway, just past the Wilson Tunnel caused police to close those lanes at Nalani'eha Street in Kalihi.

Craig Watase of Hawai'i Kai looks at the path of a boulder that landed on Anolani Street in Niu Valley today. Jeff Widener • The Honolulu Advertiser

City road crews were busy as soon as they arrived at work at 7 a.m., said Larry Leopardi, director of road maintenance. Debris along Diamond Head Road forced police to close it from about 8 to 9:37 this morning. A portion of Makiki Heights Drive near Hanahauoli School also was closed to traffic after a landslide dumped mud and cinders across both lanes.

And on 'Anolani Street in Niu Valley, a boulder roughly four feet across rolled down a hillside just after 10 a.m., crashing into a fire hydrant. Firefighters were called to shut off the hydrant while wide-eyed neighbors eyed the chunk of rock.

Crews also were trying to keep water flowing through drainage canals and along streams that usually create problems, Leopardi said.

"We are pumping water and trying to clear streams," he said. "When we have rain like this, a lot of debris sometimes clogs the inlets. We know where our choke points are."

John Cummings of O'ahu Civil Defense said the agency was activated at 4:30 this morning and was monitoring storm reports and coordinating efforts with Honolulu police and state Civil Defense officials. Cummings said O'ahu Civil Defense was operating at the "partial activation" level, meaning regular staff members were called into work early but that officials from other emergency-services providers had not been summoned to the O'ahu Civil Defense operations room in the basement of the Honolulu Municipal Building as they would be in a full activation.

Hawaiian Electric Co. said it could not say for certain if the rain was the source of several power failures, but spokesman Bruce Benson today said engineers at the utility suspected that. About 3,800 customers lost power at various times between 4 and 9 a.m. today.

A 4 a.m. electrical failure that affected about 600 customers in Kapolei closed Kapolei High School. At 4:15 a.m., nearly 1,900 customers in Makiki lost power until 5:10 a.m. when, coincidentally, 440 customers in Manoa lost power.

At 9:10 a.m. in Hale'iwa, a downed power line cut power for 863 customers along Kamehameha Highway and Hale'iwa and Pa'ala'a roads.

Verizon Hawai'i reported a higher-than-normal volume of trouble calls from all over O'ahu today because of the rain, said spokeswoman Ann Nishida. The rain killed phone service about 12:30 p.m. yesterday in Waikiki and many customers were still without service this morning, Nishida said. Congested roads hampered repair crews, she said.

"We're just asking folks to be patient," Nishida said this morning. "We will be getting to them, but we are challenged by the weather and traffic conditions."

Also, flooding of underground vaults that contain lines created problems, she said. Service often goes out when the lines get wet.

"If it is raining cats and dogs, we can't get the water out of them," she said. "A lot of times they need to wait until the rain subsides so they can pump out the manhole."

Skies over Maui were clear today after yesterday's drenching. The island's isolated southeastern coastline got the island's worst of it, with Kaupo receiving 8.5 inches of rain in a 24-hour period ending at 8 a.m. today.

Pi'ilani Highway at Pahihi Gulch in Kaupo was washed out and remained closed today, county highway officials said.

More than three inches of rain were measured at 'Ohe'o Gulch in the Kipahulu District of Halekala National Park, and 'Ulupalakua saw 2.2 inches.

More than an inch of rain dropped on Lana'i yesterday.

Moloka'i was experiencing rain this morning, but Civil Defense officials said there were no reports of flooding.