Labor Day weekend will get a soggy start Friday with scattered showers and the potential for locally heavy rainfall and flooding similar to Thursday’s deluge on Oahu.

“Friday’s looking a lot like today … primarily on Oahu but wetter on Kauai,” National Weather Service lead forecaster Chris Jacobson said Thursday night. “There’s not as much potential for heavy rain through Labor Day, but still pretty hot and humid,” with scattered showers.

A flash flood watch remains in effect for the entire state until 6 p.m. Friday, and the wet weather might linger into the weekend, the National Weather Service said.

“An upper-level trough west of the state combined with deep tropical moisture trailing south in the wake of (Tropical Storm) Ignacio (70 mph wind speed, 705 miles north-northwest of Honolulu) — those two factors combined” are responsible for the current weather pattern, said Jacobson. Because of a light southerly flow, and not tradewinds, “showers move slowly and dump a lot of rain.”

Hurricane Jimena, with wind speed of 100 mph and 690 miles east of Hilo, will continue to bring large swells to Hawaii’s east and south shores. A high-surf warning for east shores of all islands except Lanai is in effect through 6 p.m. Saturday, and a high-surf advisory for all islands’ south shores Friday morning through Saturday.

On Maui, which was under a flash flood warning midday Thursday, fire rescue crews assisted a pair of hikers trapped by flash floods in Waihee Valley at 12:48 p.m. Thursday. A man, 36, and woman, 31, visiting from Arizona were rescued by helicopter from an area near a canal above the Swinging Bridges section of the stream.

Oahu was under a flash flood warning for much of Thursday, with heavy showers and thunderstorms dumping on Honolulu and Central and Windward Oahu.

Downpours overloaded the city’s storm drain system, flooding streets and businesses in areas such as Kalihi, Iwilei, downtown Honolulu and Liliha.

“Heavy rainfall in localized areas were enough to fill our storm drain system to capacity,” city Department of Facility Maintenance Director Ross Sasamura said at a news conference held at City Hall on Thursday afternoon. “It was unable to handle any more rainfall,” which resulted in flooding.

However, he said that “the system is up to an acceptable standard,” but the city is focusing on water quality at discharge and not on a 100-year storm or global sea rise.

Rain overflowed storm drains along Iwilei Road near 11 a.m., forcing the evacuation of customers at Dole Cannery Mall and shutting down Regal Cinemas across the street. A Regal Cinemas employee said water entered the main lobby and auditoriums.

The Actors Group, located next to the mall, had some flooding but was planning to hold a preview of the play “Storefront Church” on Thursday night and the premiere Friday.

TAG President Eric Nemoto said after contending with recent flooding, he and other members built a makeshift wall with sandbags around entrances.

At Dole Cannery Mall there was ankle-deep water in some areas, and workers at R’Lax Beauty & Wellness Day Spa were pushing an inch of water out of their parlor.

Spa owner Arlax Malbog said she employs about 10 people and was unsure when she’d be able to reopen her business, especially with the expectation of more rain Thursday night.

The flooding also affected patients accessing other services on the second floor of the Cannery building, including the Eye Surgery Center of Hawaii, because of flooding near parking lots and entrances.

Center clinical director Ronald Walker said one patient was unable to get through the sandbags stacked around the front entrance, and he had to instruct her how to get into the building through a different entrance.

At a nearby Dole Cannery building, a van with a generator pumped water from a Kaiser Permanente records storage area — the second time in eight days, according to a pump operator.

Regal Cinemas and Castle & Cooke Inc., operators of Dole Cannery Mall, were unavailable for comment.

By early Thursday afternoon the Honolulu Fire Department had responded to seven water evacuations, mostly businesses in the Kalihi area but also a few homes in Aiea.

Hawaiian Electric Co. reported multiple power outages. About 1,400 customers were without power in the Pearl City/Waimalu area and about 300 near Kewalo Basin, a HECO spokesman said.

The Honolulu Department of Emergency Management said heavy ponding was reported on the H-1 and Moanalua freeways. Localized flooding was reported in Kalihi at the intersection of Dillingham Boulevard and Alakawa Street, where water was 6 to 8 inches deep, and on the H-1 westbound School Street onramp and offramp.

At Iolani Palace, water was being pumped out of the “moat” surrounding it. “We’re just trying to keep the water level down as it continues to rain,” said Kippen de Alba Chu, palace executive director. “But no damage. Water has not entered the palace at all.”

The Med-QUEST building on Dillingham Boulevard was temporarily closed due to leaking and flooding.

Sasamura said motorists, residents and businesses may file claims against the city for damage as a result of the flooding. (For information on filing a claim, call the Department of Corporation Counsel at 768-5222.)

The National Weather Service reported Aloha Tower received nearly 3 inches of rainfall from 11 a.m. to 5 p.m. Thursday, the highest reported for Oahu.

The city and the American Red Cross provided transportation and emergency shelter for the homeless living along Kapalama Canal. Bus service was provided to the shelter at Kalakaua District Park.

A homeless woman camping under a bridge was swept away with three others last week when flash flooding occurred in Nuuanu Stream. She has not been found.