The cyclone, named Sarai, is forecast to pass to the west of Fiji’s main island of Viti Levu before tracking east and passing to the south of the island.
The FCO said to follow the advice and direction of local authorities and monitor local media.
Weather updates are available on the Fiji Meteorological Service website.
Cyclone season is normally between November and April but cyclones can occur throughout the year in Fiji.
Severe weather may result in flooding, landslides, and disruption to essential services and infrastructure.