[REVISION HISTORY]

Weather variability, volcanic activity, and delayed rainy-se

Updated 46 times since CLSTR started tracking revisions of this situation.

What changed

2026-10-12 02:49 UTC → 2026-10-12 11:53 UTC · added ~~removed~~

Weather conditions across Indonesia continue to show significant variability driven by multiple atmospheric phenomena. In late August, a strong El Nino drove dry conditions in South Sulawesi, contributing to 112 forest and land fire incidents between January and August 2026. On September 8, 2026, the eruption of Gunung Anak Krakatau caused volcanic ash to spread across West Java and South Sumatra, impacting air quality and disrupting nearly 3,000 flights. By late September 2026, the Indonesian Meteorology, Climatology, and Geophysics Agency (BMKG) reported that the ENSO index reached a very strong level of +2.63, resulting in low rainfall across 87.53 percent of the country. Extreme drought has triggered widespread wildfires, particularly on Borneo, where drained peatlands are experiencing difficult-to-extinguish underground fires. As of October 9, 2026, meteorological drought persists in many regions, with 1,869 areas having experienced extreme drought through September. The onset of the 2026/2027 rainy season is expected to be delayed and shorter than usual across approximately 61.08 percent of Indonesia’s seasonal ~~zones.~~ zones, with El Nino predicted to persist until early 2027. On October ~~12,~~ 11, 2026, extreme weather in Aceh triggered flash floods and landslides in Gayo Lues and Aceh Tenggara, causing infrastructure damage and cutting off road access. While recovery efforts are underway in Gayo Lues, BMKG has issued warnings regarding the potential development of cumulonimbus clouds in parts of ~~Sumatra, Papua,~~ Sumatra and ~~maritime areas like the Malacca Strait.~~ Papua. Heavy to very heavy rainfall is predicted for Aceh, North Sumatra, West Sumatra, West Kalimantan, and parts of Papua, raising risks of flooding, landslides, and flash floods. ~~In the Jabodetabek area, Bogor, Bogor City,~~ Other regions, including parts of Java and ~~Depok are expected to experience moderate to heavy rain. While localized heavy rain is a risk, atmospheric conditions~~ Riau, remain ~~influenced by a strong El Nino and a positive Indian Ocean Dipole (IOD), which may limit moisture~~ under alert for thunderstorms and ~~maintain relatively dry conditions in certain areas.~~ strong winds.

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