A hurricane approaching Hawaii appears to have strengthened and will maintain its speed as it passes the Big Island weather officials say.
Central Pacific Hurricane Centre forecasters said Hurricane Iselle won't weaken into a tropical storm before passing over the islands as they had predicted.
Hurricane Julio, meanwhile, has followed closely behind and was expected to pass the islands over the weekend.
Hawaii has been directly hit by hurricanes only three times since 1950, though the region has had 147 tropical cyclones over that time.
The National Hurricane Centre classified Hurricane Julio as a Category 1 storm, with winds of about 120kmh. The storm was expected to strengthen slowly over the next day and a half.
The clustered storms are rare but not unexpected in years with a developing El Nino, a change in ocean temperature that affects weather around the world.
Much of Hawaii's archipelago was under a tropical storm watch or warning. Residents were stocking up on essentials, and weather officials asked the whole state to prepare for flash flooding.
The last time Hawaii was hit with a tropical storm or hurricane was in 1992, when Hurricane Iniki killed six people and destroyed more than 1,400 homes, said Eric Lau, meteorologist for the National Weather Service in Honolulu.
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 cyclones this year.
"The central Pacific doesn't see nearly the activity that the Atlantic sees," said James Franklin, chief of hurricane specialists for the centre.