An unstable weather system could keep the entire state under a flash flood watch throughout the day, and even overnight, according to the National Weather Service.
“Everywhere has the potential to be the trouble spot,” said forecaster Victor DeJesus. “It’s coming down pretty heavy on Kauaçi, Oçahu’s got more showers moving in from the south, and the Big Island is taking a beating.”

A flash flood warning for Kauai has been extended to 7:45 p.m.
Kauai County spokeswoman Mary Daubert reported that a number of roads were closed due to heavy debris and flooding.
She also said that the county’s emergency operations center had been activated and an emergency shelter opened at the Kilauea Neighborhood Center.
As of 11 a.m., the area near the Hanelei River had received nearly 10 inches of rain in the past six hours, preliminary figures from the weather service show.
A hard downpour with intermittment thunder and lightening began in
east-central Kauaçi's Wailua Homesteads about 11:30 a.m. and showed no sign
of letting up an hour later.
Power went out briefly in Wailua Homesteads.
Water poured off rooftops in sheets and flowed along some streets several
inches deep.
Earlier in the morning, before the rain started, the Wailua River was high
in its banks and low fields nearby had standing water. Water flowing over
Opaekaça Falls, a popular stop for tourists, was chocolatey brown.
Surf at Wailua Bay was brown and sloppy and at Kalapaki Bay in Lihuçe at
about 10 a.m., waves were regularly washing over the seawall on the west
side and splashing over rocks at the mouth of the bay on the east side.
Hawaiian cultural practitioners who held an overnight vigil at a heiau near
the mouth of the Wailua River through bouts of rain last night had the
cultural ceremony end in full rain.
On Oçahu, the areas of Punaluu, Kahuku and Läçie were getting rains that were heavy at times, and nuisance flooding was expected across Oçahu.
Honolulu’s Department of Emergency Management will continue to monitor this situation throughout the weekend, said spokesman John Cummings.
A special marine warning was issued for the Big Island’s southeast and windward waters, with the weather service warning of intense thunderstorms packing strong winds and frequent lightning. Boaters were advised to seek safe harbor.
Meanwhile, as of 11 a.m. Pahoa had received 3.5 inches of rain in the previous six hours.
DeJesus blamed a lingering low-pressure system in the upper atmosphere for causing all the trouble.
“That cools the temperatures aloft, the atmosphere becomes unstable and you’ve got the possibility of heavy rainfall and thunderstorms today, and possibly even into tonight,” he said.
DeJesus said the entire state remains under a flash flood watch until 6 p.m., and he added that there’s a good chance the watch will be extended.
“This thing is becoming more disorganized, and it’s starting to fall apart,” he said, referring to the weather system. “It’s weakening. But it has been uncooperative and a little bit unpredictable. Based on some of the uncertainties that have unfolded, if this continues through the afternoon, we’ll have no reason not to extend the watch throughout the night.”