Climate of Tuvalu
Tuvalu lies within the trade wind zone but on the edge of the South-west Pacific equatorial doldrum zone. Prevailing winds are from the easterly quarter and they occur most frequently between June and August. In most years from December to March, winds between the west and north usually equal or exceed the easterlies in frequency.
Wind speeds over the surrounding ocean average about 10kts. Strong winds are not common being experience about 3 percent of the time. Although Tropical Cyclones occasionally develop near to Tuvalu they rarely become hurricane force in Tuvalu waters and cause destruction on land.
Temperatures are uniformly high all year round with the mean annual temperature approximately 28 deg C.
Rainfall in the southern Tuvalu atolls is high and reliable throughout the year but less so in the northern atolls. Sixty percent of the rain falls in the November to April period and it is in this wetter season that the heaviest rates are recorded. There is a significant inverse relationship between rainfall and the El Nino/Southern Oscillation Index leading the rainfall response by several months. Most years usually have some months of abnormal rainfall, but high or low rainfalls in the southern atolls are not very common. However abnormally low rainfalls do persist longer than high rainfalls especially in the northern atolls where they can last up to eighth months.
The average duration of rainfall on Funafuti is 525 hours per year, or about six percent of the total time. It rains fifty percent more often (317 hours) during the wetter season than during the drier one (208 hours).
With the high levels of sunshine evapotranspiration rates are also high, but in most years in the south rainfall is sufficient to meet these requirements. Soil moisture deficits are most likely in the northern atolls.