Weather

Indonesia is hot and humid, and you will get used to it, particularly if you spend most of your time in air-conditioned buildings and vehicles.

Mountain areas are cooler, sometimes with overnight frost at altitude. Puncak Jaya in Papua, once one of the world's few equatorial glaciers, has all but disappeared: ice cover has shrunk by more than 95% since 1980, and BMKG expects it to vanish completely by 2026 or 2027. Do not go there expecting snow.

The rainy season runs roughly October to April, but the exact timing shifts year to year with El Niño and La Niña. 2026 is a strong El Niño year, so the dry season arrived early and is running longer and drier than average, with the next rains not reaching western Indonesia until October.

In the cities, weather stops being conversation and becomes background noise: hot and sunny, except when it rains hard, usually daily, through the wet season.

Jakarta floods most years. Reports of a fixed "five-year cycle" don't hold up; flooding is driven by individual heavy-rain days, not a schedule. January is the city's wettest month, though current official rainfall averages are not settled enough to quote here with false precision. River normalisation on the Ciliwung, Jakarta's main flood defence, is only around half finished.

Contributor: patrick

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