Rainfall

Seasonal Rainfall Outlook: October-December 2025 (OND)

Issued: 30 Sep 2025

For OND 2025, models predict above-normal rainfall over much of the Maritime Continent and eastern Mainland Southeast Asia

For OND 2025, above-normal rainfall is predicted for much of the Maritime Continent, based on the multi-model ensemble (Figure 1). The highest probability of above-normal rainfall is over the southern Maritime Continent. Most models agree on above-normal rainfall as the most likely tercile for the southern and eastern parts of the region (more than six models, Figure 2). Below-normal rainfall is predicted over the western half of the equatorial region, with most models (more than six models) in agreement over the northwestern Maritime Continent and some models (4 – 6) elsewhere. Model skill for predicting above-normal rainfall is good for the southern, central and southeastern Maritime Continent and low to moderate elsewhere. Model skill for predicting below-normal rainfall is moderate over the northwestern Maritime Continent.

For Mainland Southeast Asia, above-normal rainfall is predicted apart from over the northern region. Most models agree on above-normal rainfall over the eastern portion (more than 6 models) with only some models agreeing for the central and western portion (4 – 6 models). No dominant tercile is predicted for most of northern Mainland Southeast Asia. Model skill is moderate to good for southeastern Mainland Southeast Asia and low to moderate elsewhere in the region. 

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Figure 1: Rainfall tercile summary predictions of the multi model ensemble for OND 2025 (contains modified Copernicus C3S information).
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Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for SON 2025. Where there is no dominant tercile, it refers to the number of models with near-normal tercile (contains modified Copernicus C3S information).
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Figure 3: Average climatological rainfall's lower tercile boundary for OND based on CHIRPS (Reference period: 1991-2020).
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Figure 4: Average climatological rainfall's upper tercile boundary for OND based on CHIRPS (Reference period: 1991-2020).

The qualitative outlook is assessed for the region in general. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.
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