CLIMATE OF DIFFERENT ISLANDS AND REGIONS OF INDONESIA

CLIMATE IN DIFFERENT PARTS OF INDONESIA

Köppen–Geiger climate classification map for Indonesia

Indonesia’s generally tropical climate varies depending on location, season and altitude. Jakarta, which is lies in the coastal lowlands, has a relatively unchanging climate with heavy rainfall, low winds, high temperatures and high humidity. As Indonesia spans the Equator, it experiences no real seasons. However, in much of the country a wet season begins in November and lasts until March, followed by a dry season from April to October. Days and nights each last 12 hours. [Source: Cities of the World, Gale Group Inc., 2002, adapted from a 2001 U.S. State Department report]

Most islands remain verdant due to the frequent rainfall, which supports rainforests and intensive agriculture. However, the southeast islands, such as Flores, Sumba, Savu, Rote, Alor and Timor, lie within climate zones of Australia and are dry and relatively barren of vegetation for half the year or more. Heavy rains fall from December through March in Borneo and Sumatra. .[Source: Jill Forshee, Culture and Customs of Indonesia, Greenwood Press, 2006).

Annual rainfall in lowland areas averages 180–320 centimetres (70–125 inches), increasing with elevation to an average of 610 centimetres (240 inches) in some mountainous regions. In the lowlands of Sumatra and Kalimantan, rainfall ranges from 305 to 370 centimetres (120 to 145 inches), diminishing southward towards the northwest Australian desert. Average humidity is 82 percent. [Source: Worldmark Encyclopedia of Nations, Thomson Gale, 2007]

In Indonesia, altitude rather than season affects temperature. At sea level, the mean annual temperature is approximately 25–27 °C (77–81 °F). There is slight daily variation in temperature, with the greatest variation occurring at inland locations and at higher elevations. The mean annual temperature in Jakarta is 26°C (79°F), with an average annual rainfall of around 200 centimetres (79 inches).

Climate of Java

Average Temperature Increase in Indonesia 1981-2018: “temperature trends were obtained using BMKG observation data from 1981 to 2018. Based on the results of processing temperature trends in Indonesia, in general, temperatures in Indonesia, including minimum, average, and maximum temperatures, have a positive trend with a magnitude that varies by around 0.03 °C annually. This can be interpreted as meaning that the temperature will increase by 0.03 °C annually, so that in 30 years the location will experience an increase of 0.9 °C.”

Java features a tropical monsoon climate defined by consistently warm temperatures and two distinct seasons: a dry season (March to October) and a wet season (September to April), with some variations depending on where you are on Java. In addition, the island's rainfall and humidity vary significantly by region and topography. The mountains and plateaus are somewhat cooler than the lowlands. Temperatures in Jakarta generally range from 23°C (73°F) to 33°C (91°F). The average humidity is 82 percent, rising to 83 percent or 84 percent during the wet season. It rains about 125 days a year for an average of 180 centimeters (70 inches). The average temperature in January is 26.2̊C (79.2̊F). The temperature in July: 26.7̊C (80.1̊F) [Source: Embassy of Iran, Jakarta]

West Java, which includes cities such as Jakarta, Bandung, and Bogor, is the wettest and most humid part of Java. The region experiences a long and intense rainy season influenced by moist monsoon winds from the Indian Ocean. Areas around Bogor are especially well known for their frequent thunderstorms, with some locations recording hundreds of storm days each year. Annual rainfall in parts of West Java often exceeds 4,000 millimeters, creating lush vegetation and a consistently humid climate.

East Java, home to places such as Surabaya, Malang, and Mount Bromo, is considerably drier than the western part of the island. The influence of the Australian monsoon produces a longer and more pronounced dry season. Some coastal areas receive less than 1,000 millimeters of rain annually, giving the landscape a noticeably more seasonal character. During the dry months, skies are often clear and temperatures remain high.

Java’s Northern and Southern Coasts also differ significantly in climate. The northern coast, which faces the Java Sea, is generally flatter, hotter, and more densely populated. It experiences humid tropical monsoon conditions throughout much of the year. In contrast, the southern coast, facing the Indian Ocean, tends to be slightly cooler because of stronger ocean breezes. The south also experiences heavier and more concentrated wet-season downpours driven by moist winds from the ocean.

Surabaya has a very hot and humid climate, with an average humidity of 75 per cent and an average temperature of 27°C (81°F). The average annual rainfall is around 150 centimeters (60 inches) and the rainy season runs from November to April. The rest of the year, particularly from June to October, is drier. Periods when the monsoons change direction (usually March–April and November–December) are characterised by heavy rain and often result in flooding in East Java and Greater Surabaya. July and August are the most comfortable months of the year. [Source: Cities of the World, Gale Group Inc., 2002, adapted from a 2001 U.S. State Department report]

Rainbow Clouds in Jonggol, near Jakarta

Elevation plays a major role in shaping temperatures across Java. Lowland coastal regions remain hot throughout the year, with daytime temperatures commonly reaching 32°C to 34°C. However, temperatures decrease steadily in the volcanic mountain spine that runs across the island. Highland areas such as the Dieng Plateau and Mount Bromo are much cooler, often feeling refreshing during the daytime. Nights at higher elevations can become surprisingly cold, especially during the dry season.

Rainbow Clouds in Jonggol, near Jakarta

Rainbow clouds, a rare atmospheric phenomenon known as iridescent clouds, drew widespread attention when they appeared over Jonggol, a town about 40 kilometers south-southeast of Jakarta. The colorful display featured vivid bands of pastel hues that seemed to shimmer across the sky, prompting many residents to stop and photograph the unusual sight. Although the clouds looked almost unreal, they were the result of a natural optical process rather than digital manipulation or any extraordinary weather event. [Source: Laura Baisas, Popular Science, May 5, 2026]

Iridescent clouds form when sunlight passes through tiny water droplets or ice crystals within a cloud. As the light encounters these particles, it is diffracted, separating into different colors much like a prism creates a rainbow. According to meteorologists, the effect is most striking when the sun is partially obscured by thicker clouds or other objects, allowing the colors to stand out more clearly against the sky. Because the conditions required for iridescence are quite specific, such displays are relatively uncommon and often last only a short time.

Meteorological officials in Indonesia explained that the phenomenon observed over Jonggol involved a towering cumulus cloud. Ida Pramuwardani, Acting Director of Public Meteorology at Indonesia’s Meteorology, Climatology, and Geophysics Agency (BMKG), said that portions of the cloud blocked part of the rainbow-like effect, giving the appearance of an incomplete arc or a “rainbow cloud.” The interaction between sunlight and the cloud’s water droplets created the brilliant colors that captivated observers.

Despite their dramatic appearance, rainbow clouds are not a direct indication that severe weather is imminent. Meteorologists note that they are associated with growing convective clouds, which can signal the possibility of rain developing later. In Jonggol, the spectacle reportedly caused traffic to slow as motorists and pedestrians paused to admire and record the striking formation.

Climate of Sumatra

Jambi, Southern Sumatra month by month rainfall and average temperature Researchgate

Sumatra has a hot, humid, and equatorial climate with temperatures averaging 26°C to 32°C (73̊F to 90̊F) year-round. The island's climate varies based on topography and prevailing wind patterns and is heavily influenced by the Bukit Barisan mountain range, which runs down its western spine and acts as a massive geographic divide. Sumatra is very hot throughout the year. Fortunately the places visited by tourists tend to be in the highlands, where the climate is noticeably cooler, or near the oceans, which is tempered by sea breezes. [Source: ScienceDirect.com; agroklimatologippks.com; American Meteorological Society]

The equator crosses central Sumatra. The rainy season and dry seasons are not very distinct in northern Sumatra. The wet season runs from September to December. The hot, dry season is from May to August. In Medan the wettest months are October, November and December. The driest months are February, March and April but there isn’t that much difference between the wet months and the dry months.

Western Sumatra) is extremely wet and continuously damp. This region faces the Indian Ocean and catches the brunt of moisture-heavy monsoon clouds, creating heavy orographic rainfall. Rainfall exceeds 200 to 400 centimeters (6.6 to 13.1 feet) annually. It experiences high precipitation year-round with less defined dry seasons. The west coast of Sumatra is very wet, some places get above 400 centimeters of rain a year.

Eastern Sumatra is drier and hotter.The Bukit Barisan mountains create a "rain shadow" effect, making the eastern coastal plains (facing the Strait of Malacca) much drier than the west. Rainfall here is noticeably lower, and temperatures tend to feel more stagnant and humid.

Northern Sumatra has an equatorial climate with two distinct rainy peaks. Because the equator splits the center of the island, the northern areas experience an equatorial rainfall pattern characterized by two maximum rainy periods (often April/May and October/November). The monsoon season here often begins a month earlier than in the south.

Southern Sumatra has a monsoonal climate with pronounced wet and dry seasons. Southern Sumatra and regions extending into Region-A monsoonal zones have a more distinct dry season, usually between June and September, dominated by Australian continental air masses. In southern Sumatra the rains start in November and reach their peak in January and February.

Climate of Bali

West Bali month by month rainfall and average temperature Researchgate

Bali is located just 8 degrees south of the Equator and has a tropical, warm, and humid climate with temperatures consistently averaging between 26°C to 31°C (73̊F to 88̊F). The climate is nearly the same the year round. The temperature averages around 28̊C (82̊F) and the same amount of rain falls nearly every month. Humidity rises during the day and drops of at night. The air temperature is most delightful in the cool mornings and evenings. [Source: Bali.com, TripSavvy]

On Bali, the rainy season is between October and March; the dry season between April and October. The high season for tourists is July and August. The temperatures this time of the year are slightly cooler than the rest of the year and there are refreshing breezes coming off the sea. The low season is in the winter when the weather can be a little muggy, hot and rainy. Coastal Areas are consistently warm and more humid. The Central Highlands, including Ubud and Kintamani), are Significantly cooler, especially at night and early mornings, with higher chances of rain year-round.

The Dry Season (April to October) is the best time for outdoor activities, offering lower humidity, clear skies, and cooling coastal breezes. Rainfall is at its lowest, and days are typically sunny. The Wet Season (October to March) has higher humidity and heavier monsoonal rains, with January typically being the wettest month. Downpours can be intense but usually pass quickly, often giving way to periods of clear skies.

Climate of Nusa Tenggara, East of Bali

The wet and dry season are progressively later as one moves eastward from Bali. In some places the difference between the two seasons is very pronounced, with floods in the wet season and droughts in the dry season. On Bali, the rainy season is between October and March; the dry season, between April and September. On Lombok, the rainy season is between November and March; the dry season between May and August. The greatest rainfall is on the western side of the island.

On Komodo, the dry season lasts from May through November and wet season lasts from December to April. The rains are generally heaviest in January and February.The wet season in most of Flores is from December to April, with the dry season from May yo November. Rainfall rarely exceeds 200 centimeters. On eastern part of Flores the rainy season lasts from November to May with the heaviest rains falling in January and February. The area gets about 125 centimeters of rain a year. The rainy season in Alor lasts from October to April.

Flores has a tropical monsoon climate characterized by consistently high year-round temperatures, elevated humidity, and a distinct division between wet and dry seasons. Daytime highs : Typically range from 31̊C to 34̊C (88̊F to 93̊F) and nighttime lows usually range from 20̊C to 23̊C (68̊F to 73̊F). Humidity overs between 66 percent and 86 percent,, feeling most humid during the rainy months. The Dry Season (May to October) is the best time to visit. There is brings plenty of sunshine, minimal rainfall (averaging only 2-4 rainy days a month), and optimal conditions for trekking or diving. The Wet Season (December to March): is characterized by heavy tropical downpours and high humidity. You can expect up to 19-21 days of rain per month, which generally arrives in short, intense bursts rather than all-day washouts

The climate of Timor is influenced by the western monsoon, which brings rain, and the easterly monsoon which brings dry weather. The mountains create a rain shadow effect. The rainy season is from January to April. The dry season is May to December. The average temperature on Timor is 80 degrees F (25 degrees C). However there is great variation since in coastal regions temperatures get as high as 95 degrees F (33 degrees C) while in the high mountains it may remain relatively cool, about 70 degrees F (23 degrees C). Indeed during the months of June and July the temperature in the mountains can plummet to around 36 degrees F (5 degrees C) during the night time. During these months the mountains see steady rain fall and the air tends to be damp and humid. [Source: Andrea K. Molnar, Northern Illinois University, Department of Anthropology and Center for Southeast Asian Studies, May 2005 , seasite.niu.edu/EastTimor]

Climate of Kalimantan

Kalimantan is hot, damp and rainy throughout the year. Much of this region does not have a pronounced rainy or dry seasons. In Balikpapan rain fall amounts are high throughout the year. In other places the wettest months are October to March and the driest period is from July to September although in many cases the difference between the wet montsh and dry months are not that different.

Borneo has an equatorial and tropical rainforest climate characterized by consistently high temperatures, heavy rainfall, and high humidity year-round. The island has no traditional four seasons, but rather experiences wet and dry monsoon periods, with average daytime temperatures ranging between 27̊C and 32̊C (81̊F and 90̊F). Temperatures: Hot and stable year-round. Lows rarely drop below 20̊C (68̊F) at night, while daytime highs frequently hover around 32̊C (90̊F).). Humidity is consistently high, hovering around 80 percent throughout the year, which can make the air feel much warmer. [Source: Natural Habitat Adventures]

Rainfall is very high, averaging roughly 200 to 400 centimeters (6.6 to 13.1 feet) annually across the island. Rain can occur suddenly at any time as short, heavy tropical downpours. Because of Borneo's equatorial position, wind patterns dictate the wet and dry cycles: The Dry Season (April to September) features winds from the southwest bring slightly drier conditions. While rainfall still occurs, this is typically the sunniest and best time for trekking and wildlife spotting. During the Wet Season (October to March) the Northeast Monsoon brings heavier and more frequent rainfall. Coastal areas can experience intense downpours and rough seas, particularly between November and January.

“Average monthly rainfall in Kalimantan 2014-2020. Kalimantan experiences fire hazards almost every year, which threaten the largest tropical forest in South- east Asia. Climatic conditions, such as increasing surface temperature and decreasing rainfall, become important es- pecially when El Nino Southern Oscillation (ENSO) occurs.” Researchgate

While the entire island shares a tropical rainforest climate, topography heavily influences local weather. Coastal cities experience more distinct wet and dry shifts, whereas the island's deep interior rainforests remain persistently wet. At higher elevations the climate is significantly cooler and can sometimes drop into the single digits (Celsius).

West and North Kalimantan have a typical wet equatorial climate with no heavily pronounced dry season. They receive high annual rainfall, heavily influenced by the Intertropical Convergence Zone (ITCZ) causing year-round showers. East and South Kalimantan have more defined dry and wet seasons compared to the rest of the island. The dry season (May to October) is more prominent here, though they are prone to brief transitional wet seasons. Because they lie further south, these areas can be quite susceptible to drought during El Niño or Positive IOD weather patterns. [Source: OCHA]

Climate of Sulawesi

Sulawesi has a hot, humid tropical climate with relatively stable temperatures throughout the year. In the lowlands, temperatures generally range from 21°C to 35°C (70°F to 95°F), while the cooler highland regions average between 15°C and 30°C (59°F to 86°F). However, Sulawesi’s unusual “K”-shaped geography and rugged mountain ranges create dramatic regional microclimates. Rainfall patterns vary greatly between the island’s four main peninsulas, making some regions extremely wet while others are among the driest parts of Indonesia. The rainy season in most of Sulawesi is from November until April, with the highest rainfalls in December and January. In the southeast the wettest months are around April, May and early June. [Source: JICA, ResearchGate, OCHA]

North Sulawesi, including cities such as Manado and Gorontalo, has high rainfall amounts throughout most of the year and there is no true dry season. Even the driest months, usually from July to October, still receive considerable precipitation. The region is influenced by both the Asian and Pacific monsoons, which supply abundant moisture year-round. Annual rainfall commonly exceeds 250 centimeters (100 inches), supporting dense tropical forests and lush vegetation.

month by month rain for Makassar, southern Sulawesi Climates to Travel

South Sulawesi, home to Makassar and the highland region of Tana Toraja, has a more distinctly monsoonal climate with clearly defined wet and dry seasons. Heavy rains fall between November and April during the West Monsoon, while a pronounced dry season occurs from May to October under the influence of the East Monsoon. Rainfall totals generally range from about 150 to 300 centimeters (60 to 120 inches) annually, although mountain areas receive much more moisture than the coastal plains.

East Sulawesi, which includes Palu, Luwuk, and Kendari, is significantly drier than the rest of the island. Some areas experience what climatologists describe as an “anti-monsoonal” climate pattern. Rain-shadow effects created by surrounding mountains, especially around Palu, produce some of the driest conditions in Indonesia. Certain coastal areas receive as little as 60 centimeters (24 inches) of rainfall annually, a sharp contrast to the much wetter western and northern regions of Sulawesi.

West Sulawesi, including Mamuju and Majene, is highly humid and strongly influenced by the warm waters of the Makassar Strait. The region follows the general monsoon pattern of a prolonged wet season from November to April, but it is also subject to intense maritime squalls and heavy coastal storms. Annual rainfall commonly exceeds 300 centimeters (120 inches), making it one of the wettest sections of the island chain.

Climate of the Moluccas

The Moluccas (Maluku Islands) have a maritime tropical climate characterized by consistently high temperatures (averaging 25°C to 31°C (77°F to 88°F) year-round), high humidity, and heavy rainfall. Because the archipelago spans a vast area across the equator, its seasonal weather patterns vary by region. [Source: East of Wallace Tours]

The Moluccas have the opposite rainy season patterns as most of Indonesia. The dry season lasts from October to March. The wet season lasts from late April to September in central and southern Maluku. The wet season lasts from December to March in northern Maluku.

"Rainfall observation sites in Sulawesi and the Maluku Islands. Climatology of seasonal rainfall type is indicated as A-I (red circle), B-I (blue circle), B-II (blue diamond), and C (green triangle) types, respectively. Locations of multiple stations in Manado and Makassar (see Table S1) are a little displaced to avoid overlapping since they are very close each other." Researchgate

Central and Southern Moluccas (Ambon, Seram, Kei, Aru, Tanimbar): have a Dry Season from October to March. The Wet Season is May to August. During the wet monsoon, winds from Australia can cause heavy rainfall and rough sea conditions, which may impact inter-island ferry transport. Ambon is humid all year, receiving between 200 and 380 centimeters of rainfall annually. The wettest months occur around June (with up to 63 centimeters mm of rain), while the driest period is typically October to November. Temperatures usually range from 23°C to 31°C (73°F to 88°F) For the Central and Southern regions, the best time to visit is during the dry season from October to April, when the seas are calm and ideal for diving.

Northern Moluccas (Halmahera, Ternate, Tidore) follow a pattern closer to the rest of Indonesia, experiencing a dry monsoon from May to September and a wet monsoon from December to March. In Ternate drier conditions usually peak around August, while wet weather arrives from December through March. Temperatures consistently hover around 28 °C to 29°C (82°F to 84°F) year-round. For the Northern region, the best time to visit is during their dry season from May to September.

Climate of Papua

Much of Papua is out of range of the monsoon cycles. The wet and dry patterns are irregular, with many places getting over 200 centimeters of rain a year. The driest months tend be between May and October although heavy rains can fall in that time and often do. Along the northern coast it rainiest and often very windy from November to March. Along the southern coast it rainiest and often very windy from April to October.

rainfall in Papua Researchgate

The highlands are temperate and reasonably comfortable with mean temperatures averaging between 26°C and 15°C. The best times to visit the Baliem Valley is after March when the weather is a little drier. The lowlands are considerable hotter than the highlands. Southern Papua is located at the edge of the monsoon belt. The hottest month is December, the coolest is June. Rainfall regularly exceed 450 centimeters a year. Some places in the highlands get more than 600 centimeters a year.

The highlands of Papua do get some cold spells. In February 2006, Earth News reported: “Remote villages in Indonesia's easternmost province of Papua have been enveloped by a freak cold waves in recent weeks, resulting in cold-related ailments that have killed nearly 100 people. Temperatures dipped to as low as 41 degrees Fahrenheit in mountain communities where readings are typically above 68 degrees. Health officials say the stress caused by the cold has created outbreaks of acute pneumonia, tuberculosis, dysentery and diarrhea. Emergency cold-weather shelters were being rushed to the area, along with medical supplies. [Source: Earth News, February 22, 2006]

Image Sources: Wikimedia Commons

Text Sources: “Encyclopedia of World Cultures Volume 5: East/Southeast Asia:” edited by Paul Hockings, 1993; “Culture and Customs of Indonesia” by Jill Forshee, Greenwood Press, 2006; National Geographic, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Encyclopedia.com, Library of Congress, Indonesia Tourism website (indonesia.travel), Indonesia government websites, Live Science, The Conversation, The New Yorker, Time, BBC, CNN, Reuters, Associated Press, AFP, Lonely Planet Guides, Google AI, Wikipedia, The Guardian and various websites, books and other publications.

Last updated June 2026