Forecasters with the Central Pacific Hurricane Center say, "While the official forecast track continues to lie to the south of the Hawaiian islands, only a slight deviation to the north of the forecast track would significantly increase potential impacts to the state of Hawaii".
Early Monday, the hurricane had maximum sustained winds of about 145 miles per hour, the Central Pacific Hurricane Center in Honolulu reported.
The US National Hurricane Centre in Miami said the hurricane poses no short-term threat to land.
Swells generated by Hector are expected to reach the southeast and east shores of the Big Island and eastern Maui later Wednesday, and produce large and risky surfs.
The volcano is in the middle of a three-month eruption of lava which has been spewing since May and has covered 13.4 square miles of the island's surface.
So far, Kilauea's eruption has been ongoing for 93 days straight and more than two dozen volcanic fissures have opened up.
Tom Travis, Hawaii's emergency management administrator, said: "Hector is our first hurricane this year".
Hector was downgraded to a Category 3 storm and it's expected to continue losing steam over the next couple of days, the National Hurricane Center said. The system is now centered roughly 1300 miles east- southeast of Hilo moving toward the west.
NHC also said that Hector was about to cross into the central Pacific basin as a Category 4 storm. After that, gradual weakening is expected Monday night through Wednesday.
Hector is expected to hit Hawaii's Big Island late on Wednesday morning.
Scientists differ on how a hurricane could affect the volcano, but some say the low atmospheric pressure could help trigger eruptions.