Iona rapidly strengthened into a hurricane on Monday morning in the central Pacific Ocean and is expected to continue moving west over warm, open waters well south of Hawaii.
Iona emerged on Sunday from a tropical depression and was about 1,440 kilometres southeast of Honolulu, the US National Hurricane Centre in Miami said.
So far, the system poses no threat to the US island state of Hawaii.
No coastal watches or warnings were in effect. Iona is expected to strengthen more over the next couple of days before weakening around the middle of the week.
The hurricane has maximum sustained winds of about 120 kph. It was moving in a generally westward direction at about 17 kph.
Iona is the first named storm of the hurricane season in the central Pacific.
A second weather system has also formed in the central Pacific.
Tropical Depression Two-C is located about 1,840 kilometres east-southeast of Honolulu.
Maximum sustained winds are around 55 kph and are expected to strengthen.
