Hector also posed no immediate threat to land, but the centre said the storm's projected path could carry it just south of Hawaii by midweek.
The storm was about 1,390 miles southeast of the Hawaiian islands on Sunday and should cross into the central Pacific ocean by Sunday night or early Monday morning.
There's a possibility the two storms could merge this week: Ileana should "begin weakening later on Tuesday and dissipate or become absorbed by John on Wednesday", the National Hurricane Center said.
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.
Hurricane Hector picked up strength as it entered the Central Pacific Basin, according to forecasters.
Hurricane Hector is now 1,130 miles southeast of Big Island and moving west, according to the NHC's latest advisory.
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Even as a months-long volcanic eruption goes on, Hawaii is now on alert for a risky hurricane forecast to pass south of the islands at midweek.
Tom Travis, Hawaii's emergency management administrator, said: "Hector is our first hurricane this year". It's not known yet if the island will be impacted.
Over the next few days, Hector is expected to gradually weaken.
CNN meteorologist Haley Brink said it was too early to tell if the hurricane would trigger an eruption of Kilauea. At this far distance, it can still change directions and avoid the Big Island of Hawaii altogether, but the high speeds of a hurricane combined with the erupting Kilauea volcano is a concern.