Tongan authorities are on standby as tropical cyclone Sarai heads towards the outer islands.
The category two storm has been battering Fiji for more than two days and is expected to start affecting Tonga later today and tomorrow.
Two people have died during Sarai in Fiji, where the body of a man was found after he went missing in a river during the storm, and another drowned while swimming.
A third person has been hospitalised after being hit by a falling tree.
At its centre, Sarai's winds are reaching up to 120 km/hr, with some gusts to 170 km/hr.
The cyclone is predicted to make landfall over the Vava'u island group on Monday or Tuesday, as a category one storm.
The chief executive of Tonga's National Emergency Management Committee, Paula Ma'u, said the country was bracing for the impact of Sarai.
Mr Ma'u said his agency had been preparing people with information via radio and social media.
"They said the track of this tropical cyclone is uncertain so we have prepared the whole of the island groups, get ready and prepared for this cyclone, and yes, with emphasis on Ha'apai and Vava'u at this stage."
A Red Cross Disaster Management Coordinator, Anaseini Iotebatu, said evacuation centres were already being set up with emergency supplies.
"We have groups of volunteers in the community where they have been on standby as well," she said.
"Our relief supplies was replenished in November ... relief supplies in Tongatapu are also on standby."
Iotebatu said the Red Cross was attending regular briefings alongside other agencies including police, and the Fire and National Emergency Management Office.
Live television and radio feeds had also been set up, to keep locals informed about the unfolding situation.
"The evacuation centres have already been opened ... and welcome anybody or families who would like to make way to the evacuation centres," she said.