The climate in Fiji is tropical marine and warm year-round with minimal extremes.
Mean daily temperatures in the summer months are about 27°C, and in the winter months about 22°C. Rainfall is variable, with the warm season experiencing heavier rainfall, especially inland. At all seasons the predominant winds are the Trade Winds from the east to south-east. This causes an orographic effect, where the prevailing winds force moist air over the central mountains, dropping rain in the south east as the air rises and cools. Not only does this mean that average rainfall increases steadily inland from coastal areas in the south-east but it means that both Viti Levu and Vanua Levu experience a significant dry season in the north-west, with consequences for agriculture in those areas.
The islands lie in area which is occasionally traversed by tropical cyclones, and mostly confined between the months of November to April every year. On the average some ten to twelve cyclones per decade affect some parts of Fiji, and two to three cyclones can be very severe.
Soil moisture regimes are ustic (marked dry season >3 months), udic (dry periods always less than 90 days), perudic (similar to udic, but rainfall exceeds evapotranspiration so water moves through the soil in all months), and Aquic (soil saturated by groundwater), usually more due to poor drainage and high water table.
Two soil temperature regimes occur:
- isothermic (15-22°C and <5°C difference between winter and summer) inland above 600m altitude
- isohyperthermic (> 22°C and <5°C difference between winter and summer) below 600m altitude
