Fiji's disaster and management office are warning villagers in low lying coastal areas to prepare for the loss of crops and livestock during Cyclone Ami.
Aleki Malodali, the principal Disaster Officer, says homes, livestock and crops could be destroyed by the cyclone, which is continuing to intensify with winds of up to 170 kilometres an hour.
Fiji's weather service says that it will hit Vanua Levu, Rai and Taveuni islands either late tonight or early tomorrow.
It is then expected to curve across the low-lying Lau Island group before hitting Tonga's capital Nuku'alofa by Wednesday morning.
Mr Malodali says that villagers in low lying areas will be the worst affected and that they are told to seek shelter in higher ground.
"anything can happen that hasn't been anticipated even...... the intensity of the cyclone is expected to be very strong, especially for those farming in the low lying areas... those who have animals."
Aleki Malodali, Fiji's principal Disaster Officer.