Off the northern part of the Sumatra coast are the big islands of Simeulue and Nias and in between the archipelago of Pulau Banyak. A very deep trench in the sea west of these islands gives excellent conditions for surfing in many places. This part of Sumatra is unique with its scenery and grand nature.
The climate is tropical, but due to its many highlands, temperatures can be lower than one expects. Temperatures are approximately between 22-30 degrees Celsius. The rainfall differs from area to area, but averages 1.000-4.000mm per year. The relative humidity is 70-90% in lowlands. The year can be divided in two major seasons, dry season from February to August and wet season from September to January. However, the difference between seasons is not as big as in other parts of Indonesia. The change of season is also normally extra wet. The dry season is of course the best time for mountain climbing, to visit nature parks and for the visibility of animals, etc.
The island of Sumatra can brag lots of mammals: almost 200 reptiles, over 60 amphibians, almost 300 fish species, and more than 450 bird species. Of all these, 9 mammals, 30 fish species, and 19 bird species are endemic. The Orangutan, the Sumatran tiger, and the Sumatran rhinoceros are famous inhabitants of northern Sumatra alongside the Sumatran elephant, many species of monkeys, the Tapir, the Honey bear, and several kinds of Deer. Sumatra has also 10 species of The Hornbill, a bird noted for its enormous horn-tipped beak.
The most well known flower is the Rafflesia arnoldi, the biggest flower in the world. It is found only in certain parts of Sumatra. This plant is parasitic and grows on certain lianas but does not produce leaves. It can measure up to 1 meter in diameter and have 2 cm thick petals weighing up to 18 kg. The smell is awful.
Sea turtles have a heaven in Pulau Banyak on the west coast. The Amandangan beach on Pulau Bangkaru is the most important Green turtle rookery of Sumatra. Also Hawksbill turtles and Leatherback turtles lay their eggs here. The rare Dugong can also be seen in Pulau Banyak. The biggest island, Pulau Tuangku also probably has endemic reptiles.