Up to four cyclones could form in the Pacific this week, led by Rae, lashing Fiji as a category-two storm.
A series of low-pressure systems - from the Coral Sea in the west through to the waters south of the Cook Islands in the east - will bring disruptive weather to a long stretch of the blue continent.
As of Monday afternoon, Tropical Cyclone Rae is impacting Fiji's east, including the Cakaudrove, Lomaiviti and Lau provicinces.
Philip Duncan, head weather analyst at Weather Watch, said the storm could yet strengthen into a category three storm.
"Over the next couple of days it moves further out to sea," he said on Monday.
"It looks as though Tonga should be mostly away from it ... this is tracking very close to Tonga as well and hopefully it remains offshore," he said.
Fiji Broadcasting Corporation reports schools are closed and evacuation centres are open in affected areas, with no reports yet of severe damage beyond blocked roads.
Two cyclones have developed in waters near Australia: category-two Bianca in the Indian Ocean, which is likely to stay well clear of Western Australia's coast, and Alfred in the Coral Sea.
Two other low-pressure systems which have the potential to reach cyclone-strength.
The 96P system is just east of Vanuatu and tipped to move steadily south and east closer to Fiji, while the 92P will move further south or Cook Islands, well away from populated islands.
"There's a lot of life and energy," Mr Duncan said of the region.
There was still a high degree of uncertainty around Alfred, presently a category-one storm but likely to form into a more destructive category-three system, Mr Duncan said.
"That is the one to monitor the most and the one most likely to affect people," he said.
Weather forecasts have Alfred moving down Queensland's coast through the week, with the possibility of it impacting Queensland's south-east or New Caledonia.
