Rainfall
Monthly Rainfall Outlook: December 2025
Issued: 28 Nov 2025
For December 2025, above-normal rainfall is predicted over the northeastern and southern Maritime Continent as well as eastern parts of Mainland Southeast Asia.
For December 2025, below-normal rainfall is predicted over parts of the central and western Maritime Continent based on the multi-model ensemble (Figure 1), with above-normal rainfall over northeastern and parts of the southern regions. Most models (more than six models, Figure 2) predict above-normal rainfall as the dominant tercile for the northeastern regions and below-normal rainfall as the dominant tercile over central Borneo.
For Mainland Southeast Asia, above-normal rainfall is predicted over eastern most region and a mix of below-normal rainfall and no dominant tercile elsewhere. Most models predict above-normal rainfall for the eastern region, and at least some models (4 – 6) predict below-normal rainfall over the northeastern and southern most regions.
Model skill is good for predicting above-normal rainfall over the northeastern Maritime Continent and southeastern Mainland Southeast Asia. Model skill is low to moderate elsewhere in Southeast Asia.
Figure 1: Rainfall tercile summary predictions of the multi model ensemble for December 2025 (contains modified Copernicus C3S information).
Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for December 2025. Where there is no dominant tercile, it refers to the number of models with near-normal tercile (contains modified Copernicus C3S information).
Figure 5: Average climatological rainfall's lower tercile boundary for December based on CHIRPS (Reference period: 1991-2020).
Figure 6: Average climatological rainfall's upper tercile boundary for December 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.