Oahu will remain under a flash-flood watch through this afternoon following a rain-soaked Sunday that saw a storm-related fire knock out power to parts of Ala Moana Center on the last shopping weekend before Christmas, the closure of the Honolulu Zoo and City Hall, an overwhelmed sewer system that burst manhole covers and wrong-way drivers trying to avoid flooded streets.

A 4-foot-wide sinkhole opened up on Oahu Avenue yesterday.

At least three flooded homes received help from the Hawaii chapter of the American Red Cross.

A 150-pound boulder rumbled off Diamond Head and landed at the Diamond Head Lighthouse.

The rain unleashed a handful of mudslides, including one at Farrington Highway at Ko Olina that choked the only way into and out of the Leeward Coast.

And Kalanianaole Highway was shut down in both directions near the Makapuu Lighthouse because of flooding and loose construction equipment. Traffic was being turned around in Hawaii Kai and Waimanalo.

The road reopened at 7:15 p.m.

"This storm system is saturating everything," said Peter Hirai, deputy director of the city’s Department of Emergency Management. "You’ve got asphalt starting to buckle and deteriorate and minor rockslides. Our storm drain system is designed to carry water out, but it’s not doing it, so manholes are popping up."

THE STORM system that hit Kauai Saturday night and pounded Oahu yesterday was expected to deluge Maui and the Big Island last night, dropping 5 inches of snow in a 24-hour period at the 12,000-foot level of 13,000-foot Mauna Kea, National Weather Service forecaster Matt Foster said.

And Oahu could still get more rain today.

"It’s not going to be a sunny day by any means," Foster said. "There could be other bands of moisture moving through. There could still be heavier showers."

Honolulu officials warned drivers to stay put yesterday as gauges across the southeastern half of Oahu showed rain falling at 1.5 inches to 3 inches per hour — with even more rain continuing to bear down on Oahu from the south.

Over the 24-hour period ending at 5 p.m. yesterday, Honolulu Airport received 5.3 inches of rain, breaking the previous rainfall record of 5.28 inches set in 1955.

Many of those who ignored the warning to stay home saw their cars flooded at overwhelmed intersections and found themselves stuck in traffic on Kalanianaole Highway near the Makapuu Lighthouse; the H-1 freeway westbound heading to the Vineyard offramp (ponding water); the entrance to Campbell Industrial Park (flooding); and Farrington Highway.

Those who opted for TheBus had little better luck from Hawaii Kai to Waimanalo when buses were detoured because of the Kalanianaole Highway blockage.

Throughout the day, Honolulu police who were not blocking overwhelmed manhole covers — in Kailua, Kalihi, Punchbowl Street and South King and Richards streets — reported motorists repeatedly driving the wrong way on congested roads trying to get around blocked traffic.

Oahu remained under a flash-flood warning for much of yesterday, meaning that flash flooding was imminent or occurring in streams, roads and low-lying areas, and people were urged to move to higher ground.

The flash-flood watch issued for the entire island chain through today means that conditions exist that could lead to flash flooding.

Oahu residents awoke yesterday to pounding rain that barely let up.

Then at 7:30 a.m., rain seeped into equipment at Hawaiian Electric Co.’s Makaloa substation, causing a "flash over" that knocked out electricity to nearby condos, the Neal Blaisdell Center and parts of Ala Moana Center, darkening an estimated 45 stores including Macy’s and Shirokiya.

"Essentially there was too much water to run off, and it was able to penetrate some of the equipment," said HECO spokesman Peter Rosegg. "That proceeded to smoke and smolder and trigger a big fire."

HECO crews diverted electricity from normal power lines to restore service to all customers by 11 a.m., Rosegg said.

No one was hurt, and HECO officials were still assessing the cost of the damage yesterday.

Ala Moana Center officials said all stores were reopened by noon.

The Honolulu Academy of Arts canceled its free Bank of Hawaii Family Sunday. City officials closed the Honolulu Zoo and all municipal golf courses — and the West Loch and Ewa Villages courses and Hanauma Bay will remain closed today.

Officials also closed Honolulu Hale early last night during Honolulu City Lights because of the weather.

And the last night of the annual Pearl Harbor Festival of Lights holiday boat tours was canceled. More than 1,500 visitors turned out for the half-hour tours Friday and Saturday nights, officials said.

The state Health Department issued a brown-water advisory for Oahu and Kauai, urging people to avoid waters possibly contaminated with runoff.

And all of the rain might have contributed to other problems:

» 85,000 gallons of untreated wastewater flowed into Kuapa Pond in Hawaii Kai.

» A 12-inch water main break also forced the temporary closure of McCully Street between Lime Street and Kapiolani Boulevard.

» A sewage pipe broke near 2010 9th Ave. in Palolo, spilling 4,000 gallons of waste water into Palolo Stream.

» The state Department of Health said sewage manholes also overflowed in Kaneohe, Kailua and into Honolulu Harbor.