Rainfall
Monthly Rainfall Outlook: August 2026
Issued: 31 Jul 2026
For August 2026, below-normal rainfall is predicted over most of the southern ASEAN region and southern Mainland Southeast Asia.
For August 2026, below-normal rainfall is predicted over the southern ASEAN region, based on the multi-model ensemble (Figure 1). The highest probability of below-normal rainfall is over the central and eastern equatorial region, where most of the models (more than six models, Figure 2) predict below-normal rainfall as the dominant tercile. Model skill for below-normal rainfall is good over the eastern equatorial region and moderate elsewhere over the Maritime Continent.
For the northern ASEAN region, below-normal tercile is predicted for parts of southern Mainland Southeast Asia and southern Philippines, with above-normal tercile or no dominant tercile predicted elsewhere. There is good agreement between models (more than six models) for the coast of western Mainland Southeast Asia and southern Philippines, with some agreement between the models (four to six models) elsewhere in general. Model skill is low over both southern and eastern Mainland Southeast Asia.
Figure 1: Rainfall tercile summary predictions of the multi model ensemble for August 2026 (contains modified Copernicus C3S information).
Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for August 2026. Where there 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 August based on CHIRPS (Reference period: 1991-2020).
Figure 4: Average climatological rainfall's upper tercile boundary for August 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.