UPDATE: 8:05 a.m.
Radar shows that the heavy rain that had been soaking Oahu this morning has ended, the National Weather Service said.
However, a flash flood watch remains in effect for the entire state through 6 p.m. today.
Heavy rain, especially over East Oahu, has prompted a flood advisory for the entire island through 10 a.m.
Radar at 6:58 a.m. showed heavy rain near Waimanalo falling at 2 inches per hour, the National Weather Service said.
Locations in the advisory include, but are not limited to, Honolulu, Hauula, Waimanalo, Kaneohe Marine Base, Hawaii Kai, Laie, Palolo, Kahaluu, Ahuimanu, Punaluu, Salt Lake and Kailua.
A flash flood watch remains in effect for all islands through 6 p.m. today.
The rainy weather also kept first responders and electrical repair crews busy through the night.
Honolulu firefighters responded to multiple calls throughout the night and early morning hours of downed trees caused by the thunderstorm.
Firefighters responded to 11 calls in Leeward and Central Oahu from about 11:30 p.m. Monday to 4:15 a.m. today, according to Honolulu Fire spokesman Capt Scot Seguirant.
Of the 11 calls, firefighters responded to six downed trees in Ewa Beach, one in Nanakuli, three in Waipahu and one in Mililani.
Hawaiian Electric Co. also responded to lightning-related outages.
Crews were dispatched to Makaha Valley at about midnight where about 675 customers suffered a power outage.
HECO restored power at approximately 2 a.m. but another round of lightning occurred more than an hour later where lightning struck a pole in the valley, causing the same customers to lose power again.
Crews are working to restore power, said HECO spokeswoman Shannon Tangonan.
Accessibility to the damaged pole is challenging and it may take until this afternoon to complete pole replacement work.
HECO is also responding to four transformers impacted by the lightning that affected some customers in Kahuku, Hauula and Waipahu.
The earlier flash flood warning for Oahu has expired but a flash flood watch is in effect for all islands through this afternoon.
An upper-level-low will hover over the western Hawaii Islands through most of the day before moving east, according to the National Weather Service. The resulting unstable conditions across the islands could produce locally heavy rainfall and flash flooding.
A flash flood warning for Oahu is in effect ntil 2:30 a.m.
At 11:36 p.m., radar indicated areas of heavy rainfall associated with developing thunderstorms across multiple portions of Oahu, according to the National Weather Service. Heavy rainfall across southwestern and windward portions of Oahu are spreading northward and may affect the entire island within the next hour or so. Flash flooding is expected to begin shortly.
Flooding is expected in drainage ditches, streams, rivers, roads, properties and other low-lying areas. Public road closures are possible in some areas. Landslides are possible in steep terrain.
A flash flood watch for all Hawaiian Islands remains in effect through Tuesday morning due to unstable conditions brought by an upper-level low-pressure system moving over the western side of the state.
The system brings the potential for locally heavy rainfall and flash flooding.
Forecasters say increased thunderstorm activity is possible statewide through early this evening due to the instability. There are also increased chances of rain for the leeward side of the Big Island and Maui.
Today’s forecast calls for mostly cloudy skies, with numerous showers and thunderstorms on the windward side, and scattered showers and thunderstorms on the leeward side. Locally heavy rainfall is possible.
Highs range from 81 to 86 degrees Fahrenheit, with east winds of 15 to 20 mph. Lows tonight range from 68 to 73 degrees.
A flash flood watch means conditions are favorable for flash flooding, which is life threatening, and officials warn the public should not cross fast-flowing water by vehicle or foot.
The unsettled weather pattern will persist across the island chain through Tuesday, forecasters said, with locally heavy rainfall and thunderstorms possible statewide. More stability is expected Tuesday night, but showers and a wet tradewind pattern are expected to continue through the weekend.
Breezy to windy trades are expected from Thursday through Saturday.
Surf will be 6 to 10 feet along north shores, and 4 to 6 feet along west shores through Tuesday. Surf along south shores will be 2 feet or less today and 1 to 3 feet Tuesday.
Surf along east shores will be 3 to 5 feet today, lowering to 2 to 4 feet on Tuesday.
A north-northwest swell is expected to fill in tonight and peak on Tuesday, with a larger, west-northwest to northwest swell arriving Wednesday. Forecasters say that swell will reach high surf advisory thresholds along north and west shores from late Wednesday through Thursday, and may peak near warning levels.
Surf along east shores may also near advisory levels by the end of the week.
More record highs, meanwhile, were set over the weekend. On Sunday, a record high of 87 degrees at Hilo surpassed the previous one of 86 set in 1970. A record high of 92 degrees at Kahului passed the previous one of 89 set in 1992. On Friday, a record high of 89 degrees was set in Hilo, breaking the old record of 85 in 2015.