Hurricane Iselle's outer edges brought rain and wind to Hawaii on Thursday as it was poised to become the first hurricane or tropical storm to hit the island chain in 22 years. Another hurricane closely followed.
Iselle was expected to pass overnight across the Big Island, one of the least populated islands, then send rain and high winds to the rest of the state on Friday.
"We're primarily urging residents to still take proper precautions to prepare themselves to keep everyone safe," National Weather Service meteorologist Eric Lau said.
Hundreds of people flowed into emergency shelters as some communities lost power.
Hurricane Julio strengthened into a Category 3 storm and followed Iselle's path with sustained maximum winds of 115 mph (185 kph). It was about 1,000 miles (1,600 kilometres) behind Iselle and projected to head just north of the islands sometime early Sunday.
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, Lau said.
Hawaii Gov. Neil Abercrombie said the state is prepared for the back-to-back storms.
At least 30 flights were cancelled Thursday from several airlines, the Hawaii Tourism Authority said.
As residents prepared, a 4.5-magnitude earthquake struck the Big Island but didn't cause major damage. There were no reports of injuries.
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 this year.