The state was bracing last night for heavy rain — and even some hail and snow — as a winter storm soaked Kauai and began to work its way down the island chain.

The National Weather Service issued a severe thunderstorm watch for Kauai County, Oahu and their surrounding waters through 2 a.m. today.

In addition to heavy rain, the storms could bring winds exceeding 60 mph and hail an inch in diameter or larger, the weather service said.

The rest of the state remained under a flash-flood watch through 6 a.m. tomorrow.

"What we have is a very powerful storm system that is bringing heavy rain and a line of powerful thunderstorms over Kauai and Oahu," said Tom Birchard, National Weather Service lead forecaster. "Right now there may be some nuisance flooding (on Oahu), but it could get serious tonight or tomorrow. It’s passing Kauai and inching toward Oahu."

The storms are ahead of a front that will pass late today or early tomorrow, with a return to tradewinds by Sunday, Birchard said.

The summits of Mauna Loa and Mauna Kea will be under a winter storm watch from this evening to tomorrow morning, the weather service said. Heavy snow could fall as summit temperatures are expected to dip below freezing tonight as moist air moves up from the south, the weather service said.

Haleakala was under a wind advisory through 6 a.m. today, as gusts as high as 50 mpg buffeted the Maui summit.

Heavy rain began falling on Kauai early yesterday evening, Kauai County spokeswoman Mary Daubert said Hanalei Bridge was closed at 7:25 p.m. as rainwater ponded or ran swiftly across roadways all over the island. Some areas had power outages.

On Oahu, police were clearing debris off roadways, winds ripped a termite fumigation tent off a house and parts of Kailua last night were reported without power.

John Cummings, Oahu Civil Defense spokesman, said the city is on alert for potential flooding. City crews have been clearing streams in preparation for winter storms and were out again today in the Kailua area, he said.

The city also will open its Emergency Operations Center if the flash flood watch is upgraded to a warning.

Today is a furlough day for city employees, but Mayor Peter Carlisle said workers will be called if necessary.

"Essentially people will be on standby unless there is an emergency situation, and then they will be rolled out to take appropriate action to address the emergency and to make sure that people are safe and taken care of," Carlisle said.

The expected intense downpours, which could result in flash flooding, are the result of an "unstable atmosphere" created by abundant moisture, a cold front and a deep upper-level trough northwest of the islands, forecaster Tim Craig said.

There is a chance of scattered showers for Sunday morning’s Honolulu Marathon. The forecast calls for partly sunny skies with a high near 75 and east winds around 9 mph.