Indonesia is the world's largest archipelago, spanning over 5,000 kilometres from the tip of Sumatra to the eastern edge of Papua. With more than 17,000 islands straddling the equator, the country has some of the most stable year-round temperatures on Earth — but also some of the most dramatic variation in rainfall between wet and dry seasons, and between one island and another.
Climate
Indonesia is equatorial and tropical. Daytime temperatures in the lowlands are remarkably consistent throughout the year, typically 27–33°C, with overnight lows rarely below 23°C. What varies dramatically is rainfall: some parts of West Sumatra receive over 5,000 mm per year while parts of eastern Nusa Tenggara see less than 1,000 mm. This difference is driven by the monsoon reversal and the position of islands relative to the prevailing wind flow.
The country has two seasons — a wet season and a dry season — rather than the four seasons of temperate climates. The timing depends on which side of the equator you are on. In Java, Bali and most of Sumatra (south of the equator or at it), the wet season runs roughly from November to March and the dry season from April to October. In northern Sulawesi and northern Sumatra (above the equator), the pattern shifts.
Because Indonesia sits near the equator, it is outside the main typhoon and tropical cyclone tracks. Severe storms that affect the Philippines or Vietnam rarely reach the Indonesian archipelago. However, intense monsoon rainfall and the country's steep volcanic terrain combine to make landslides and flash floods the most significant weather-related hazard, particularly during peak wet-season months.
Seasons
Wet season (south) (November – March)
In Java, Bali, Lombok and most of Sumatra, this is the main rainy season. Morning skies often start clear before clouds build through the afternoon into thunderstorms, with heavier continuous rain possible. Humidity is consistently above 85%. January is usually the wettest month. Rivers rise, waterfalls are at their most impressive, and landscapes turn a vivid green — it is a beautiful time of year despite the rain.
Transition (April)
The wet season ends in Java and Bali through April, with rainfall tapering off. Temperatures remain steady. This is one of the best months for trekking and beach holidays — dry enough to enjoy outdoor activities, but still green rather than dusty.
Dry season (May – September)
The main dry season across southern Indonesia. Rain is rare (though not impossible), humidity drops noticeably, and skies are often cloudless. Bali is at its most comfortable for beach holidays and temples. This is the high season for tourism. In Nusa Tenggara and Papua, the dry season is more pronounced and some areas become quite brown and dusty by September.
Early wet season (October – November)
Rainfall returns gradually through October. Afternoon showers become frequent before the full wet season sets in. This is a quieter shoulder season for tourism with generally manageable weather.
Extreme weather events
Indonesia's most significant weather-related disasters are flooding and landslides triggered by monsoon rains on the country's steep volcanic terrain. The 2007 Jakarta floods displaced around 340,000 people. More recently, heavy rain in January 2020 submerged parts of Jakarta under more than 2 metres of water in the worst flooding in more than a decade. Drought during strong El Niño years (2015, 2019) has fuelled major forest and peat fires in Sumatra and Kalimantan, producing regional haze that affected the entire region.
Regional variation
Sumatra is mountainous, volcanic and very wet, especially along the western coast. Padang receives over 4,000 mm of rain per year. The island has a classic wet/dry monsoon split but rainfall is high all year.
Java, the most populous island, has the clearest wet/dry split. Western Java (Jakarta, Bandung) is wetter than eastern Java (Surabaya, Banyuwangi). Highland areas like Bandung and Malang are significantly cooler than the coast.
Bali sits in the rain shadow of Java and has a more pronounced dry season than either Java or Lombok. Southern Bali (Kuta, Seminyak, Nusa Dua) is drier and hotter than the central highlands around Ubud.
Nusa Tenggara (Lombok, Komodo, Flores, Timor) gets progressively drier as you move east. Komodo island is one of the driest parts of Indonesia with a long dry season that turns the landscape savanna-like.
Sulawesi and the Maluku islands have a more complex climate because of the central mountain ranges; different sides of the islands see different wet seasons. Papua is mostly wet year-round with rainforest climate.
Best time to visit
For most travellers, the best time to visit Indonesia is May to September, during the dry season. Bali, Java, Lombok and Komodo are at their best in these months. July and August are peak tourist season — expect crowds and higher prices. If you want to avoid crowds, May–June and September are excellent compromises. Avoid January and February for outdoor-focused trips unless you genuinely enjoy rain. The Komodo dry season (June–September) is particularly rewarding because the islands become accessible and water visibility for diving is excellent.
Climate facts
- Indonesia straddles the equator, so technically one side of the country can be in wet season while the other is dry at the same moment.
- Jakarta is one of the fastest-sinking cities in the world — partly due to groundwater extraction, but worsened by monsoon flooding. The capital is being moved to Nusantara in East Kalimantan over the coming decades in part because of this.
- Bandung, in the highlands of West Java, is nicknamed "Paris van Java" partly because of its cooler colonial-era climate, with average highs around 26°C compared to Jakarta's 32°C.
- The Indonesian archipelago contains some of the wettest places on Earth — several stations in West Sumatra and West Papua record over 5,000 mm of annual rainfall.