location of the only settlement, Edinburgh of the Seven Seas, and the agricultural area of Potato Patches. The highest point is the summit of a volcano called Queen Mary's Peak at an elevation of , high enough to develop snow cover in winter. The other islands of the group are uninhabited, except for a weather station with a staff of six on Gough Island, which has been operated by South Africa since 1956 and has been at its present location at Transvaal Bay on the southeast coast since 1963. Climate The archipelago has a Cfb, wet oceanic climate, under the Köppen system, with mild temperatures and very limited sunshine but consistent moderate-to-heavy rainfall due to the persistent westerly winds. Under the Trewartha classification, Tristan da Cunha has a humid subtropical climate due to the lack of cold weather. The number of rainy days is comparable to the Aleutian Islands at a much higher latitude in the northern hemisphere, while sunshine hours are comparable to Juneau, Alaska, 20° farther from the equator. Frost is unknown below elevations of , and summer temperatures are similarly mild, never reaching . Sandy Point on the east coast is reputed to be the warmest and driest place on the island, being in the lee of the prevailing winds. Flora and fauna Many of the flora and fauna of the archipelago have a broad circumpolar distribution in the South Atlantic and South Pacific Oceans. For example, the plant species Nertera granadensis was first collected in Tristan da Cunha, but has since been recorded as far away as New Zealand. Invasive species The islands of Tristan da Cunha have a high significance of global biodiversity: two of them, Gough and Inaccessible, form a UNESCO natural World Heritage Site. This designation is largely due to the seabird population found there. The biodiversity of the island is vulnerable to introduction of invasive species. Due to Tristan da Cunha's isolated archipelago ecology, and increase of tourism with cruise ships and research vessels, invasive species are a particular concern for Tristan da Cunha. The islands' vegetation and mammal species are not equipped to defend against or control introduced species, increasing island vulnerability, due to lack of defensive behavioural mechanisms and slow generational output rates. Efforts to decrease and eradicate invasive flora, fauna, and marine species have been undertaken, including a programme aimed at eradicating predatory invasive mice on Gough Island. The