A tropical depression near Wallis and Futuna has a 50-50 chance of becoming a cyclone, and affecting Samoa and Tonga this weekend and early next week.
Forecasters say the cloud bands associated with the depression will definitely affect Samoa and Wallis.
A cyclone forecaster at the Fiji Metservice, Terry Atalifo, says it is very slow moving system.
He says the depression itself is likely to start hitting Samoa late Sunday, or even Monday.
"If it happens to be a cyclone, Samoa will experience very heavy rain, wind will be very gusty as well. Flooding of low-lying areas will be a concern for them. But as this system moves further south, it poses more threat to Tonga. Fiji will experience the outer cloud bands of this system, but in terms of winds, we are not looking at cyclone force winds."
Police officers in Samoa, including those who are taking local leave, have been called to report immediately for duties as the country prepares for strong gale force winds.
The acting chief executive officer of the Ministry of Health, Pelenatete Stowers, has issued advice for the public to take safety measures in preparing food and to boil water because of flooding.