Seasonal Forecast for March – May 2026
Updated 06 March 2026
Under the prevailing Northeast Monsoon, the northern and southern ASEAN regions continue to experience their traditional dry and wet seasons respectively as the monsoon rainband is located south of the Equator, with prevailing low-level winds blowing from the northwest or northeast over the region. While showers are typical over the southern ASEAN region, occasional dry conditions can be expected since the region is currently experiencing the dry phase of the Northeast Monsoon. Around late March or early April, the prevailing low-level winds gradually weaken and become light and variable in direction as the Northeast Monsoon transitions into inter-monsoon conditions.
For March 2026, below-normal rainfall is predicted for parts of the central and western Maritime Continent, while above-normal rainfall is predicted for the northeastern Maritime Continent. For March – May 2026, the above-normal rainfall is predicted to persist, along with below-normal rainfall for much of the rest of the Maritime Continent. La Niña conditions are predicted to weaken in February 2026 and transition to ENSO-neutral conditions in March 2026. La Niña events tend to bring wetter conditions to parts of Southeast Asia. Above-normal temperature is predicted for most of the ASEAN region for MAM 2026.
Under the prevailing dry conditions, hotspot and smoke haze activity in the northern ASEAN region is likely to remain elevated, with a heightened risk of transboundary smoke haze occurrence, particularly over the northwestern parts of the Mekong sub-region where below-normal rainfall is forecast. While overall hotspot activity is likely to remain subdued under the prevailing wet weather conditions over the southern ASEAN region, hotspot activity may still increase, accompanied with smoke plume development, during the dry phase of the Northeast Monsoon conditions, particularly in areas where below-normal rainfall is predicted.
The qualitative outlook is assessed for the region in general and based on the latest runs from models provided by the SEA RCC-Network LRF node. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.
For March 2026, below-normal rainfall is predicted for parts of the central and western Maritime Continent, while above-normal rainfall is predicted for most of the northeastern Maritime Continent.
For March 2026, below-normal rainfall is predicted over parts of the central and western Maritime Continent, while above-normal rainfall is predicted over most of the northeastern Maritime Continent based on the multi-model ensemble (Figure 1). For the northeastern and central Maritime Continent regions, most of the models (more than six models, Figure 2) predict above-normal and below-normal rainfall, respectively, as the dominant tercile, while only four to six models agree on below normal rainfall over the western and southwestern region. Model skill is good for predicting above-normal rainfall over the northeastern Maritime Continent and moderate for below-normal rainfall over the western and central Maritime Continent.
For Mainland Southeast Asia, there is little agreement between the models for most of the region with no dominant tercile being predicted. Model skill is low to moderate for much of the region.
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| Figure 1: Rainfall tercile summary predictions of the multi model ensemble for March 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for March 2026. Where there no dominant tercile, it refers to the number of models with near-normal tercile (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological rainfall’s lower tercile boundary for March based on CHIRPS (reference period: 1991-2020). | Figure 6: Average climatological rainfall’s upper tercile boundary for March 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. More outlook and verification plots, including for tercile and quintile probabilistic forecasts for rainfall, are in the “Model products and verification: NCEP, ECMWF, UK Met Office” on the SEA-RCC Network LRF Node webpages.
For MAM 2026, above-normal rainfall is predicted over most of the northeastern Maritime Continent and below-normal rainfall for much of the rest of the Maritime Continent.
For MAM 2026, an increase in chance of above-normal rainfall is predicted for most of the northeastern Maritime Continent, with an increased chance of below-normal rainfall for most of the rest of the Maritime Continent, based on the multi-model ensemble (Figure 1). For above-normal rainfall, most models (more than six models) agree for the region of higher confidence, with some models (4 – 6 models) predicting above-normal rainfall for the rest of the region. For below-normal rainfall, most models (more than six models) are in agreement for the central and southwestern Maritime Continent, with at least some of the models (4 – 6 models) agreeing for the rest of the region. Model skill is good over the northeastern Maritime Continent for predicting above-normal rainfall, and moderate to good for below-normal rainfall elsewhere over the Maritime Continent.
For Mainland Southeast Asia, near-normal rainfall and no dominant tercile are predicted for most of the region, with below-normal rainfall for the northwestern parts of the region . Model skill is moderate to good for central and southern Mainland Southeast Asia, and low for northern Mainland Southeast Asia.
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| Figure 1: Rainfall tercile summary predictions of the multi model ensemble for MAM 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for MAM 2026. Where there no dominant tercile, it refers to the number of models with near-normal tercile (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological rainfall’s lower tercile boundary for MAM based on CHIRPS (reference period: 1991-2020). | Figure 6: Average climatological rainfall’s upper tercile boundary for MAM 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. More outlook and verification plots, including for tercile and quintile probabilistic forecasts for rainfall, are in the “Model products and verification: NCEP, ECMWF, UK Met Office” on the SEA-RCC Network LRF Node webpages.
For March 2026, above-normal temperature is predicted over most of the Maritime Continent and western Mainland Southeast Asia.
For March 2026, above-normal temperature is predicted over most of the Maritime Continent and western Mainland Southeast Asia, with the highest likelihood over the eastern Maritime Continent, based on the multi-model ensemble (Figure 1). Most of the models (more than six models, Figure 2) predict above-normal temperature as the most likely tercile for most of the mentioned regions. Elsewhere, below- to near-normal tercile is predicted (Figure 1). Model skill for predicting above-normal temperature is relatively good for the Maritime Continent, and moderate for Mainland Southeast Asia.
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| Figure 1: Temperature tercile summary predictions of the multi model ensemble for March 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for March 2026. Where there no dominant tercile, it refers to the number of models with near-normal tercile (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological temperature for March based on ERA5 (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. More outlook and verification plots, including for tercile and quintile probabilistic forecasts for temperature, are in the “Model products and verification: NCEP, ECMWF, UK Met Office” on the SEA-RCC Network LRF Node webpages.
For MAM 2026, above-normal temperature is predicted over most of the ASEAN region.
For MAM 2026, above-normal temperature is predicted over most of the Maritime Continent (Figure 1). Most models (more than six models) predict above-normal temperature as the most likely tercile over this region (Figure 2). Model skill for predicting above-normal temperature is good for the Maritime Continent.
For Mainland Southeast Asia, above-normal temperature is also predicted over most of the region (Figure 1), except for the southeastern parts where near-normal temperature is predicted. Most models agree on above-normal temperature as the most likely tercile for much of western Mainland Southeast Asia, with some models (4 to 6 models) agreeing on the most likely tercile elsewhere in the region (Figure 2). Model skill for Mainland Southeast Asia is moderate to good for predicting above-normal temperature and low to moderate for predicting near-normal temperature.
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| Figure 1: Temperature tercile summary predictions of the multi model ensemble for MAM 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for MAM 2026. Where there no dominant tercile, it refers to the number of models with near-normal tercile (contains modified Copernicus C3S information). |
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| Figure 5: Average climatological temperature for MAM based on ERA5 (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. More outlook and verification plots, including for tercile and quintile probabilistic forecasts for temperature, are in the “Model products and verification: NCEP, ECMWF, UK Met Office” on the SEA-RCC Network LRF Node webpages.
Frequently Asked Questions
What is a seasonal forecast?
A seasonal forecast provides forecast information about the general weather conditions at seasonal timescales up to several months ahead. Long range predictions rely on predicting components of the atmosphere and the oceans which show variations at large spatial and temporal scales. Among these key components is the sea-surface temperature – an important indicator in the El Niño Southern Oscillation (ENSO) cycle.
Example of probabilistic long range forecast using the multi-model ensemble. For areas nearby Peninsular Malaysia, the forecast is showing a probability of 50-70% of rainfall being in the below-normal (33%) tercile range. (Source: WMO LC LRF)
To account for the chaotic nature of the atmosphere, seasonal forecast adopts a probabilistic approach and the forecast weather condition is presented as an average over an extended period of time, usually with reference to climatology.
ASMC carries out monthly seasonal forecast predictions based on various seasonal model forecasts from the leading meteorological centres, supplemented by individual assessments from respective countries in South East Asia. The skillfulness of seasonal forecast relies greatly on the performance of seasonal models, which differ from one place to another and for different seasons of the year.
Receiver operating characteristic (ROC) score of UK GloSea5 seasonal hindcast for above-normal precipitation scenario for Dec – Feb (left) and May – Jul (right) over Asia region. Higher ROC score (indicated in red) means better model skill. (Source: UK Met Office)
For example, one way to assess the seasonal model skills is to examine the ROC score. From the figures above, we can see that ROC score map differs greatly from one season to another. During the period from Dec to Feb, a high ROC score region is observed mainly over the Philippines whereas during the period from May to Jul, a high ROC score region is observed over the near equatorial region such as Peninsular Malaysia and Sumatra.