Cyclone Daman, currently rated at the lowest Category 1 cyclone level, could dump 250 millimeters (10 inches) of rain and pack wind gusts up to 135 kilometers (85 miles) an hour over northern Fiji from Friday morning, duty forecaster Matt Boterhoven said.
That will mean considerable damage to local houses, trees and gardens and flooding from the first cyclone of the season in southwest Pacific region, he said.
Nadi Weather Office Director, Rajendra Prasad, said the cyclone was moving south at about 10 kilometers (6 miles) an hour.
Damaging winds up to 100 kilometers (60 miles) an hour and heavy rain were expected over the outlying island of Rotuma from Thursday night until late Friday, he said.
Northern outer island groups, the Yasawas and Mamanucas, and western and northern parts of Fiji 's main islands were expected to feel the direct effect of the cyclone later Friday, he added.
Cyclones - called typhoons in much of Asia and hurricanes in the Western hemisphere - are large-scale rotating storms that generate high winds and typically form at sea before moving inland.
The tropical storms are common in the South Pacific from November to April and range from category 1 to category 5. The most powerful can pack sustained winds of 210 kilometers (132 miles) an hour.