Indonesia Weather, climate and geography

Weather and climate

Best time to visit

Indonesia is split by the equator, which results in a tropical climate across the archipelago with relatively even temperatures year-round. Inland and around the mountainous regions, temperatures average at 26°C (79°F) while the coastal regions averaging 28°C (82°F). While temperatures are relatively constant, rains do not follow the similar pattern. In general, Indonesia also has two monsoon seasons: the northeast monsoon (December to March) and the southwest monsoon (June to September). These monsoon seasons either bring an abundance of rainfall or a dry spell, depending on the geographical region you are visiting.

Jakarta: the sprawling capital of Indonesia is situated on the northwest coast of Java and is sheltered from the south-west monsoon. Jakarta has a tropical monsoon climate and is characterised by one long wet season, which runs from October to May and a short dry season, which runs from June throughout September. Year-round, the temperature is warm, with an average high temperature of 31°C (88°F) and an annual average low temperature of 26°C (79°F). The prime time to experience Jakarta is from June to mid-October, during the dry season when the skies are clear.

Bali: Bali allures tourists with its beautiful beaches, forested volcanic mountains and cultural sites. Located a few degrees south of the equator, this island experiences a tropical climate throughout the year. The rainy season is from November to May while the relatively dry season (some showers are still likely) is from June to October. The dry season is a good time to see Bali at its best, as there is little rain, low humidity and plenty of sunshine, with an average high of 31°C (88°F). Avid surfers can enjoy Bali's breaks all-year-round, but the best months for surfing is during the dry season.

Sumatra: the island of Sumatra receives abundant rainfall throughout the year. Medan, the capital of North Sumatra province, has a tropical climate with no real dry season, although February is slightly drier than the other months. Palembang, the capital of South Sumatra province, also sees plenty of rain throughout the year, although July is slightly drier than the other months.

Required clothing

Given the year-round tropical climate and humidity of Indonesia, lightweight and loose clothing, including cottons and silks, are recommended. Rainwear is essential, and a jacket might be needed due to the rough winds along the coast or in the mountains. Warmer clothes can be necessary for the cooler evenings and highland areas – thicker cotton and woollen garments work best. It is regarded as inappropriate for swimwear to be worn anywhere other than the beach or at sports facilities. To avoid sunburn or sunstroke, wearing a hat and sunscreen are advised. When visiting temples or other religious sites, you should wear clothing that covers your arms, shoulders and legs.

Geography

Indonesia lies between the mainland of Southeast Asia and Australia in the Indian and Pacific oceans. It is the world's largest archipelago country. Indonesia is made up of five main islands - Sumatra, Java, Sulawesi, Kalimantan (part of the island of Borneo) and New Guinea - and 30 smaller archipelagos.

In total, the Indonesian archipelago consists of about 18,307 islands according to the National Institute of Aeronautics and Space; 6,000 of these are inhabited and stretch over 4,828km (3,000 miles), most lying in a volcanic belt with more than 400 volcanoes, the great majority of which are extinct. The landscape varies from island to island, ranging from high mountains and plateaux to coastal lowlands and alluvial belts.

The high incidence of volcanoes in Indonesia is due to its location along a stretch of the Pacific Ring of Fire. The collision of various tectonic plates means that around 90% of the world's earthquakes occur within this area, with Indonesia suffering from frequent earthquakes and volcano eruptions.