UPDATE 10:45 p.m.

A flood watch is in effect from Thursday morning through Saturday afternoon for all Hawaiian islands.

National Weather Service forecasters say “significant flooding may occur due to the overflow of streams and drainages across the state. Roads may also be closed, along with property damage in urban or low lying spots due to runoff. Landslides may also occur in areas with steep terrain.”

The weather service said “areas of particular concern include east and southeast sections of the Big Island, where washout of roads could isolate communities.”

“A kona low is expected to bring widespread heavy rainfall to the islands from Thursday into the weekend. Heavy rainfall will begin Thursday on the Big Island, spreading to the remaining islands Thursday night through Saturday. Heavy rainfall rates for an extended amount of time are expected to result in flash flooding, particularly over already saturated areas,” the flood watch says.

7 p.m.

The flood advisory for the Big Island has been extended to 10 p.m.

The National Weather Service reported heavy rain over leeward Big Island with the heaviest rain falling around Kawaihae and areas north of Waikoloa Village. Rain was falling at a rate of 1 to 2 inches per hour.

Flood caused by excessive rainfall is possible. Some locations that will experience flooding include Waikoloa Village, Kawaihae, Kohala Ranch, Puako, Kamuela, Mauna Lani, Waikoloa Beach and Mahukona.

5 p.m.

The Big Island is under a flood advisory through 7 p.m. tonight. The National Weather Service reported heavy rain over leeward Big Island near Waikoloa Village and Puuanahulu. Rain was falling at a rate of 1 to 2 inches per hour and will likely continue through the afternoon.

Previous coverage

A flood watch has been issued for all main Hawaiian islands from Thursday morning to Saturday afternoon.

The National Weather Service said a kona low is expected to bring widespread heavy rainfall to the islands from Thursday into the weekend.

Forecasters expect the heaviest rainfall to begin Thursday on Hawaii island and then spread to the remaining islands Thursday night through Saturday.

Heavy rainfall rates for an extended amount of time are expected to result in flash flooding, particularly over already saturated areas. Flooding may also occur due to the overflow of streams and drainages and landslides may also occur in areas with steep terrain.

A flood watch means conditions are favorable for flash flooding, which is life threatening. The public should be prepared to take action should flash flood warnings be issued.

Temperatures over Big Island summits are also expected to drop near or below freezing, prompting a winter storm watch from Thursday morning through Saturday afternoon.

Forecasters say total snow accumulations greater than 6 inches is possible, with wind gusts as high as 70 mph.

Travel to the summits could be very difficult to impossible, and should be postponed until the weather improves.

A high surf advisory, meanwhile, remains in place for the east-facing shores of Kauai and Oahu, with breaking waves of 7 to 10 feet, through 6 p.m. today.

Kauai County Ocean Safety officials have posted box jellyfish warning signs at Salt Pond Beach Park, and advise the public to avoid swimming on south- and west-facing shores.