A heavy rain alert is now in force Yasawa and Mamanuca Groups, Momi-Nadi-Lautoka-Ba-Tavua-Rakiraki, Kadavu and nearby smaller islands, as well as the Lau and Lomaiviti Groups.
The Nadi weather office states an active trough of low pressure is expected to move in from the west, bringing significant weather changes starting later Friday.
The forecast predicts occasional rain, heavy at times, accompanied by a few thunderstorms across the affected areas.
Authorities are warning residents and visitors to brace for localised heavy rainfall that could lead to flash flooding in low-lying and flood-prone areas. Motorists are advised to exercise caution due to poor visibility on roads during heavy rain or thunderstorms.