La Niña Expected to Arrive in Indonesia by End of 2025, Bringing Potential for increased Rainfall
Indonesia is bracing for the arrival of La Niña, a climate phenomenon known to trigger excessive rainfall, with predictions indicating its presence by the end of 2025. The anticipated shift in weather patterns comes as the country monitors the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD).
According to a report released by the Meteorology, Climatology and Geophysics Agency (BMKG) on Thursday, October 2nd, the ENSO currently exhibits a neutral tendency throughout 2025. Tho, a growing number of global climate models suggest a potential for a weak La Niña to develop towards the close of the year.
La Niña differs significantly from its counterpart, El Niño, which is characterized by elevated Pacific Ocean temperatures.Instead, La Niña is defined by cooler-than-average sea surface temperatures in the equatorial Pacific ocean. A senior official stated that these cooler temperatures can contribute to increased rainfall across numerous regions of Indonesia.
Currently, the Indian Ocean Dipole (IOD) is in a negative phase and is expected to remain so until November 2025. This, combined with the potential arrival of La Niña, suggests a heightened probability of wetter conditions.
Longer and Earlier Rainy Season Anticipated
The BMKG’s 2025/2026 rainy season forecast indicates that the upcoming season will likely be longer than usual and may begin earlier than historically observed in most areas. The peak of the rainy season is projected to occur between November and December 2025 in western Indonesia, and January to February 2026 in the southern and eastern regions.
The onset of the rainy season will not be uniform across the archipelago. Approximately 47.6% of Indonesia’s territory,encompassing 333 season zones (ZOM),is predicted to experience the start of the rainy season between September and November 2025. Some areas of Sumatra and Kalimantan have already begun to experience rainfall before September 2025.
Furthermore, the rainy season is predicted to advance or arrive earlier than the average climatological conditions in most parts of Indonesia, affecting 294 ZOM, or 42.1% of the country.
Despite the potential for increased rainfall, the overall accumulation during the 2025/2026 rainy season is generally expected to fall within the normal category, meaning rainfall levels will likely be consistent with typical patterns – neither significantly wetter nor drier than usual.
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the BMKG continues to monitor these climate indicators closely and will provide updated forecasts as the situation evolves.
Why is this happening? The arrival of La Niña, coupled with the negative phase of the Indian Ocean Dipole (IOD), is driving the expectation of increased rainfall in Indonesia. La Niña brings cooler-than-average sea surface temperatures in the Pacific, while the negative IOD contributes to wetter conditions over Indonesia.
who will be affected? The entire Indonesian archipelago is expected to be impacted, though the timing and intensity of rainfall will vary regionally. western Indonesia is predicted to experience peak rainfall between November and December 2025, while the south and east will see peaks in January and February 2026. Approximately 47.6% of the country’s territory will experience the start of the rainy season between September and November 2025.
What is the expected outcome? A longer and possibly earlier rainy season is anticipated. While overall rainfall accumulation is expected to be within normal ranges, the increased rainfall could lead to flooding and landslides in vulnerable areas.
**How will this unfold
