Climate of Indonesia

The climate of Indonesia is almost always warm and wet because it is a tropical country. The warm waters around Indonesia keep temperatures on land almost the same all year. Coastal areas are usually around 28 °C (82 °F), while mountain areas are cooler, about 26 °C (79 °F). In the very highest mountains, temperatures can drop to around 23 °C (73 °F). The weather does not change much through the year, and the difference in daylight between the longest and shortest day is very small—only forty-eight minutes.

The biggest change in Indonesia’s climate is how much rain falls. The air is very humid, between 70 and 90% moist, and the winds change direction through the year, bringing rain from different places. From June to September, winds come from the south and east. From December to March, they come from the northwest. Big storms and typhoons are rare, but fast currents in narrow channels like the Lombok and Sape straits can be dangerous.

Indonesia has many different climate zones. Most of the country has a tropical rainforest climate, which gets the most rain. Other areas have tropical monsoon and tropical savanna climates, which are drier. In some high mountains, you can find oceanic climates and subtropical highland climates. Even higher up, in places like the Papuan highlands, the climate can be as cool as a tundra climate or subpolar oceanic.

Monsoons

The rain patterns in Indonesia change because of something called the Australian-Indonesian monsoons. There are two main seasons: a dry season from April to September and a rainy season from October to March. These seasons change because of air moving from Australia, Asia, and the Pacific Ocean.

Local winds can also change these patterns, especially on some central islands. The winds and rain shift because Indonesia is between two large land areas. Sometimes, winds from far away change direction and bring rain when they meet humid breezes from the Indian Ocean. This helps create the rainy season in many parts of the Malay Archipelago. See also monsoon trough.

Prevailing winds

Wind patterns and local geography change how much rain falls across Indonesia. The western and northern areas, like Western Sumatra, Java, Bali, and parts of Kalimantan, Sulawesi, and Papua, receive lots of rain—over 2,000 millimeters each year. Some rain comes from moist air caught by tall mountains.

Areas closer to Australia, such as Nusa Tenggara and the eastern part of Java, are drier, with some places getting less than 1,000 millimeters of rain each year. In the southern Malukus, rain can be hard to predict because of local winds.

Temperature

See also: Climate

The air temperature in Indonesia stays about the same all year and doesn’t change much from place to place. It gets cooler when you go higher up. For every 90 meters you climb, the temperature drops by about 1 °C. In some very high mountains, it can get cold enough at night for frost. The tallest mountains in Papua are always covered in snow.