Fiji metservice says it is monitoring a tropical disturbance that has formed north-east of Vanuatu.
It says the system is slowly moving in an eastward direction and there are no associated winds with the system.
But the lead forecaster at the Fiji met service, Shalwin Singh, says heavy rain is associated with the tropical disturbance and that should affect Fiji's Rotuma.
He says they won't know for a few days as to whether it will turn into a tropical cyclone.
"So in terms of forming into a tropical cyclone, we are going for a moderate probability till Monday and from Tuesday onwards, we are going for a high probability it forming into a tropical cyclone."
Shalwin Singh says if it turns into a cyclone, it will be very close to Samoa.