Tuvalu has westerly gales and heavy rain from November to March and tropical temperatures moderated by easterly winds from April to November. The land is very low-lying, with narrow coral atolls. The highest elevation is 4.6 metres (15 ft) above sea level on Niulakita.
Tuvalu consists of three reef islands and six true atolls. Its small, scattered group of atolls have poor soil and a total land area of only about 26 square kilometres (less than 10 sq. mi) making it the fourth smallest country in the world.
The islets that form the atolls are very low lying. Nanumanga, Niutao, Niulakita are reef islands and the six true atolls are Funafuti, Nanumea, Nui, Nukufetau, Nukulaelae and Vaitupu. Tuvalu's Exclusive Economic Zone (EEZ) covers an oceanic area of approximately 900,000 km2.
Funafuti is the largest atoll of the nine low reef islands and atolls that form the Tuvalu volcanic island chain. It comprises numerous islets around a central lagoon that is approximately 25.1 kilometres (15.6 miles) (N–S) by 18.4 kilometres (11.4 miles) (W-E), centred on 179°7'E and 8°30'S. On the atolls, an annular reef rim surrounds the lagoon with several natural reef channels.
Surveys were carried out in May 2010 of the reef habitats of Nanumea, Nukulaelae and Funafuti and a total of 317 fish species were recorded during this Tuvalu Marine Life study. The surveys identified 66 species that had not previously been recorded in Tuvalu, which brings the total number of identified species to 607.