For September 2026, below-normal rainfall is predicted over most of the Maritime Continent based on the multi-model ensemble (Figure 1). The highest probability of below-normal rainfall is over the southern half of the Maritime Continent. However, most of the models (more than six models) predict below-normal rainfall as the dominant tercile for most of the Maritime Continent, apart from the northwestern Maritime Continent, where a slight increase in chance of above-normal rainfall is predicted, and parts of the northeastern Maritime Continent, where much of the models predict below-normal rainfall (four to six models). Model skill for below-normal rainfall is good over the southern half of the Maritime Continent and low to moderate elsewhere. Model skill for above-normal rainfall over the northwestern Maritime Continent is low to moderate.

For Mainland Southeast Asia, a slightly increase in chance of below-normal rainfall is predicted for most of the region (Figure 1), apart from northern and southeastern Mainland Southeast Asia where there is little to no agreement between the models (Figure 2). Much of the models (four to six) are in agreement for the regions of Mainland Southeast Asia where below-normal rainfall is predicted based on the multi-model ensemble. Model skill is low to moderate for predicting below-normal rainfall over Mainland Southeast Asia

Rainfall

Rainfall

Monthly Rainfall Outlook: September 2026