Hawaii island is under a tropical storm warning; Maui County and Oahu are under tropical storm watches; and the entire state is covered by a flash flood watch as two hurricanes east of Hilo Wednesday pack a potential one-two punch of heavy rain, high surf and powerful winds.

The warning is in effect for the Big Island and surrounding coastal waters

Both Hurricane Iselle and Hurricane Julio  are expected to weaken into tropical storms by the time they near Hawaii waters. But Iselle, which is still forecast to hit the Big Island Thursday, and Julio, which is predicted to veer north of Hawaii island and Maui Sunday, are serious threats that have government officials warning the entire state to prepare for severe weather through the weekend.

Forecasters said those under a warning should complete preparations to protect life and property. A warning is issued when a hazardous weather event is occurring, imminent or likely.

The flash flood watch begins at 4 a.m. Thursday and lasts until 6 a.m. Saturday. The tropical storm watch means that tropical storm conditions are likely within the next 48 hours.

Hurricane Iselle was about 695 miles east-southeast of Hilo at 7 a.m. Wednesday, moving west-northwest at 15 mph, with maximum sustained winds near 85 mph and stronger gusts. Hurricane force winds extend up to 35 miles from the center, and tropical storm force winds extend up to 140 miles,

Iselle weakened slightly overnight, from maximum sustained winds of 100 mph late Tuesday, and  is expected to weaken to a strong tropical storm later Wednesday. Its projected track, as of 5 a.m. Wednesday, still has it hitting Hawaii island Thursday, but shifted slightly to the south from late Thursday’s projection.

“The tracks of Iselle and Julio are definitely a call to prepare,” state Emergency Management Administrator Doug Mayne said Tuesday. “Our goal isn’t to scare anyone, but we want to make sure Hawaii’s citizens and visitors have what they need to stay safe and healthy. People should have their emergency plans and seven-day kits in place and consider preparing their homes and businesses for high winds and flooding.”

Stores throughout the state reported long lines as shoppers heeded the advice and bought up supplies of water, toilet paper, flashlights and batteries.

State officials also closed parks and schools in the projected path of the storm.

Iselle continues to weaken as it moves over cooler waters and encounters wind shear. The storm’s sustained winds were 140 mph on Monday.

Another storm, Julio, grew into a hurricane late Tuesday and is following a similar path as Iselle. But forecasters expect it to also weaken and become a tropical storm when it nears Hawaii Sunday.

The current track has Iselle moving over Hawaii island Thursday as a tropical storm with 30 to 60 mph sustained wind and higher gusts and locally heavy rains statewide of 5 to 8 inches.

The storm is also expected to move south of Maui County starting Thursday night with 30 to 45 mph winds and higher gusts in some places. Oahu and Kauai should see tropical weather conditions Friday with 30 to 45 mph winds and gusts of up to 70 mph.

“It is important not to focus too closely on the exact track and intensity forecasts because the average track error 72 hours out is about 100 miles, the average intensity error is about 15 knots (17 mph), and because the hazards of a tropical cyclone can extend over a broad area often well away from the center,” the National Hurricane Center said.

Surf generated by Iselle is expected to reach the islands by Wednesday, and possibly becoming damaging by Thursday. Forecasters expect to issue a high surf advisory Wednesday. The surf coincides with high tides from the approaching full moon.

“Extremely rough surf conditions are expected to accompany the passage of Iselle near the vicinity of Oahu overnight Thursday into Friday,” forecasters said. 

The Coast Guard is urging mariners to prepare for the onset of heavy weather and storm surge and surf of 10 to 15 feet by securing boats and equipment.

Forecasters issued a tropical storm warning for Hawaiian waters 40 to 240 nautical miles out to sea because of stormy seas.

Forecasters project that Hurricane Julio will weaken into a tropical storm and track north of the islands starting on Sunday.

As with Iselle, the forecast foe Julio can vary significantly as conditions change over the next few days.

The storm was about 1,650 miles east of Hilo at 5 a.m. Wednesday, moving west-northwest at 17 mph.

Two big storms so close together in the eastern Pacific are rare but not unexpected in years with a developing El Nino, a change in ocean temperature that affects weather around the world.

“It’s certainly pretty rare,” Franklin said. “The central Pacific doesn’t see nearly the activity that the Atlantic sees.”

When an El Nino develops, “those are the kinds of years you see more activity,” he said.

“You get more activity so the risk of impact goes up in El Nino years,” James Franklin, the chief of hurricane specialists.

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The Associated Press contributed to this story.