Bulletin

13 NOV 2025

ASEAN Climate Outlook Forum

Twenty Fifth Session of the ASEAN Climate Outlook Forum (ASEANCOF-25)

27 – 30 October 2025, Online

Twenty Fifth Session of the ASEAN Climate Outlook Forum (ASEANCOF-25)

The Twenty-fifth session of ASEANCOF (ASEANCOF-25) was organised by the Ministry of Water Resources and Meteorology, Cambodia (MOWRAM), RIMES, ASMC, the ASEANCOF Working Group, UN ESCAP, and WMO. Participants from the NMHSs of ASEAN Member States created a consensus forecast for the boreal winter monsoon 2025/2026 in the ASEAN region. The consensus for the December-January-February (DJF) 2025/2026 outlook was achieved through an online session, which included presentations from different NMHSs, questionnaires, and discussions regarding the current climate conditions and predictions for Southeast Asia. The theme of ASEANCOF-25 was on advancing the tailoring of climate services to better meet the diverse needs of users across the ASEAN region. On the last day of ASEANCOF-25, a sharing session was held which included a panel discussion on the various uses of climate services.  

CONDITIONS AND OUTLOOK

Recent (September – October 2025) sea surface temperatures (SSTs) were below-average across the central and eastern equatorial Pacific Ocean and, along with atmospheric indicators such as stronger trade winds and increased cloudiness in the western Pacific, indicate La Niña or La Niña-like conditions. In the Indian Ocean, a negative Indian Ocean Dipole is present.

International climate outlooks predict weak or moderate La Niña conditions for December 2025 to February 2026. After DJF 2025/2026, most models indicate a transition from La Niña to ENSO-neutral conditions, although there remains a possibility that La Niña may persist beyond early 2026. The Indian Ocean Dipole (IOD) is likely to return to neutral during December 2025.

The onset of the 2025/2026 Northeast monsoon season has been or is expected to be near- or later than average for much of the northern ASEAN region. The onset for much of the southern ASEAN region is predicted to be near-average. The strength of the Northeast Monsoon is predicted to be near-average over most of Southeast Asia.

During DJF 2025/2026, tropical cyclone frequency is predicted to be above average around the Philippine Sea, and near-average for the Bay of Bengal, and South China Sea.

​RAINFALL

For the upcoming boreal (Northern Hemisphere) winter season (DJF 2025/2026):

Over the Maritime Continent, near- to above-normal or above-normal rainfall is predicted for much of the eastern half of the region, including most of the Philippines, Brunei Darussalam, Sabah, and Timor-Leste. One exception is over the northwestern Philippines where below- to near-normal rainfall is predicted. For the western half, most of the region is predicted to experience either below- to near-normal or near-normal rainfall, including near-normal rainfall over Singapore, Peninsular Malaysia, and parts of East Malaysia.

Across Mainland Southeast Asia, near- to above-normal rainfall is predicted over parts of southern Mainland Southeast Asia, including southern Thailand, southern and eastern Cambodia, southern Viet Nam, as well as central Myanmar. Near- to below-normal rainfall is predicted over northern parts, including northern Myanmar, Lao PDR, and Viet Nam. Elsewhere, near-normal rainfall is predicted.

TEMPERATURE

For the upcoming boreal (Northern Hemisphere) winter season (DJF 2025/2026):

Over the Maritime Continent, near-to above-normal or above-normal temperature is predicted, apart from over the northern Philippines where near-normal temperature is predicted.

Over Mainland Southeast Asia, most of the region is predicted to experience near-normal temperature, apart from northern Myanmar, northern Thailand, central and southern Lao PDR, and most of Cambodia where near-to above-normal or above-normal temperature is predicted.

The following maps provide the probabilistic outlooks for DJF 2025/2026 season in terms of tercile categories of “Above Normal” (AN: upper tercile), “Near Normal (NN: middle tercile) and “Below Normal” (BN: lower tercile).

[1]   For this outlook, near-to above-normal temperature corresponds to 50% probability of above-normal temperature, 40% near-normal, and 10% below-normal.  Further information is in the consensus maps.