Hawaii has been directly hit by hurricanes only three times since 1950. The last time Hawaii was hit with a hurricane or tropical storm was in 1992, when Hurricane Iniki killed six people and destroyed more than 1,400 homes in Kauai, Lau said.
Hawaii Gov. Neil Abercrombie said the state is prepared for the back-to-back storms, noting the National Guard is 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 by federal emergency management officials.
State Attorney General David Louie promised that Saturday's primary elections, including congressional and gubernatorial races, will go forward as planned.
As residents prepared for the possible one-two punch of storms, a 4.5-magnitude earthquake struck the Big Island but didn't cause major damage. There were no reports of injuries.
Travelers faced disrupted plans when at least 50 flights were canceled Thursday from several airlines, including Hawaiian Airlines, Delta, United, Air China and WestJet, the Hawaii Tourism Authority and airlines said.
American Airlines and US Airways canceled flights in and out of the Big Island and Maui after 6 p.m. Thursday through noon Friday. Commuter airline Island Air canceled some afternoon flights and shut down all operations Friday.
Hawaiian Airlines canceled some inter-island flights for Thursday evening and moved its Maui-Los Angeles flight up by nearly five hours. The airline waived reservation change fees and fare differences for passengers who needed to alter their plans Thursday and Friday.
Other attractions also announced plans to stay closed for all or part of Friday, including the Royal Hawaiian Center mall in Waikiki and the Polynesian Cultural Center near Oahu's north shore.
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 the wide swath of the Pacific Ocean that includes Hawaii could see four to seven tropical storms this year.
Associated Press writers Oskar Garcia, Cathy Bussewitz and Manuel Valdes in Honolulu; Karin Stanton in Kailua-Kona; Doug Esser in Seattle; Dan Joling in Anchorage, Alaska; and Brian Skoloff in Phoenix contributed to this report.