"Whoop, there goes the power," 29-year-old Andrew Fujimura, of Puna, said yesterday. "It's fine. We'll just go to bed early tonight."
Fujimura was trading videos with a friend in Maui to help the friend see what weather conditions to expect. The videos show loud winds blowing through palm trees, white foamy waves chopping high on to shoreline shrubs and rocks - even a surfer riding rolling waves with an overcast sky on the Big Island's eastern shore.
Waves of 5m to 7m were breaking, Fujimura said.
"I can't say I'm too worried," he said. "Worst-case scenario, the power may go out a day or two. But we're prepared for that kind of stuff."
Emergency officials on the Big Island sent a warning to nearby residents after a geothermal plant accidentally released an unknown amount of steam containing hydrogen sulfide, a smelly, poisonous compound. Crews were working to control the release and monitor the emissions, while nearby residents were urged to evacuate if they experience discomfort, Hawaii County Mayor Billy Kenoi's office said.
It was not clear whether the release was directly linked to the storm.
Forecasters were analysing storm data before making possible changes to its categorisation, National Weather Service meteorologist Eric Lau said.
"We're primarily urging residents to still take proper precautions to prepare themselves to keep everyone safe," Lau said.
Hundreds of people flowed into emergency shelters set up at high schools on the Big Island, one of which lost power. Crews worked to restore electricity to the shelter in Pahoa with at least 140 people.
Power also was lost yesterday in two communities on the Big Island: Waimea, a town of about 9200 people near the island's north shore, and Puna, a district scattered with residents south of Hilo, Hawaii County Civil Defence officials said.
Mayor Billy Kenoi said that no major injuries or damage from the first bits of wind and rain had been reported.
But heavy rains led authorities on the Big Island to issue a flood advisory.
On Maui, power to a water treatment plant went out, prompting county officials to ask Kula residents to conserve water.
People prepared for the storm by making last-minute trips to the store and boarding up windows at their homes.
"It's getting more windy, and it's raining pretty good," said Denise Laitinen on the Big Island.
"But I'm ready for it. Everything outside is secured, and I've boarded up the picture windows. I feel good about being prepared for anything these storms bring us."
Meanwhile, Hurricane Julio strengthened into a Category 3 storm and followed Iselle's path with sustained maximum winds of 185 km/h.
It was about 1600km behind Iselle and projected to head just north of the islands sometime tomorrow.
Hawaii has been directly hit by hurricanes only three times since 1950. The last time the state was hit with a hurricane or tropical storm was in 1992, when Hurricane Iniki killed six people and destroyed more than 1400 homes in Kauai, Lau said.
Hawaii Governor Neil Abercrombie said the state was prepared for the back-to-back storms, noting the National Guard was at the ready and state and local governments were closing offices, schools and transit services across Hawaii.
"What we're asking the people to do now is pay attention, stay focused and listen to the directions," he said.
"Hunker down with your family and friends and ride out the storm."
Abercrombie said President Barack Obama had been briefed on Hurricane Iselle.
State Attorney-General David Louie promised that the weekend's primary elections, including congressional and gubernatorial races, would go ahead as planned.
As residents prepared for the possible one-two punch, a 4.5-magnitude earthquake struck the Big Island but didn't cause major damage. There were no reports of injuries.
Kelsey Walker said the quake felt like a "little jolt" but didn't knock things off shelves at the Waimea grocery store where he works.
"We have a hurricane. Now we have this on top of it. What else?" Walker mused.
Travellers faced disrupted plans when at least 30 flights were cancelled yesterday from several airlines, including Delta, United, Air China and WestJet, the Hawaii Tourism Authority said.
American Airlines and US Airways cancelled flights in and out of the Big Island and Maui.
After high winds hit Maui, California couple Rudy Cruz and Ashley Dochnahl left the island earlier than planned, getting to Oahu but failing to secure a flight back home.
"We were trying to beat it, but we now will have to ride it out," Cruz said.
The storms are rare but not unexpected in years with a developing El Nino, a change in ocean temperature that affects weather around the world.
Ahead of this year's hurricane season, weather officials warned that the wide swath of the Pacific Ocean that includes Hawaii could see four to seven tropical storms.
- AP
