Tropical Cyclone Pam has been upgraded to a category three as it moves in a southwesterly direction in waters between Vanuatu and Fiji.
In Solomon Islands, a tropical cyclone warning is in force for Temotu, Malaita and Makira provinces, with the east of the country being warned to expect heavy rain, gale force winds and high seas in the next 24 to 48 hours.
Pam is to the east of Temotu province and moving southwest at a rate of five knots and is further intensifying.
In Vanuatu, all vessels have been ordered to stay in port and sailings from Port Vila and from Luganville in Santo are on hold until further notice.
People in Fiji are being warned not to go to sea this week as Pam moves closer to their islands.
Fiji's weather authorities say the system does not pose a direct threat to Fiji but from today until Friday there will be heavy rain and thunderstorms as well as moderate to rough seas.
People in flood prone areas are also being warned of flash flooding.