Vanuatu's tropical depression is expected to intensify as it moves southeast towards Fiji.
A low to the southeast of Santo has brought heavy rain cloud and thunder to the island group.
A strong marine warning remains in place.
A forecaster at Vanuatu's Meteorological Services, David Gibson, says people have been told to take precautions.
"At the moment, there's a tropical low just to the south east of Santo the biggest island. In the short term its moving south east and with that it creates a lot of cloud and rain mostly above the northern parts and central parts of Vanuatu, and with that we are expecting flooding as well, of low lying areas."
The Honolulu-based Joint Typhoon Warning Center has already indicated the strong possibility of this low system near Vanuatu becoming a cyclone.