Rainfall
Monthly Rainfall Outlook: October 2025
Issued: 30 Sep 2025
For October 2025, above-normal rainfall is predicted over most of the Maritime Continent and much of Mainland Southeast Asia.
For October 2025, above-normal rainfall is predicted over most of the Maritime Continent based on the multi-model ensemble (Figure 1), apart from over much of the western part. Most models (more than six models, Figure 2) predict above-normal rainfall as the dominant tercile for the southern and eastern region. Most models (more than six models ) predict below-normal rainfall over the northwestern Maritime Continent.
For Mainland Southeast Asia, above-normal rainfall is predicted over much of the region. Most models (more than six models) predict above-normal rainfall over the eastern part, with some models (4 – 6) predicting above-normal rainfall over central Mainland Southeast Asia. Elsewhere, no dominant tercile is predicted.
Model skill is good for predicting above-normal rainfall over the southern Maritime Continent, low to moderate for predicting above-normal rainfall elsewhere in Southeast Asia, and low to moderate for predicting below-normal rainfall over the western Maritime Continent.
Figure 1: Rainfall tercile summary predictions of the multi model ensemble for October 2025 (contains modified Copernicus C3S information).
Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for September 2025. Where there is no dominant tercile, it refers to the number of models with near-normal tercile (contains modified Copernicus C3S information).
Figure 3: Average climatological rainfall's lower tercile boundary for October based on CHIRPS (Reference period: 1991-2020).
Figure 4: Average climatological rainfall's upper tercile boundary for October 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.