Seasonal Forecast for January 2026 – March 2026
Updated 12 January 2025
Northeast Monsoon conditions are expected to continue across the ASEAN region, with the monsoon rainband positioned south of the Equator. During this period, the prevailing winds across the northern ASEAN region typically blow from the northeast or east. In the southern ASEAN region, the light and variable wind conditions experienced in December 2025 typically transition westerly to northeasterly winds. These prevailing winds may further intensify at times during the Northeast Monsoon surge. The northern and southern ASEAN region experiences dry and wet weather conditions respectively during this period. Towards the end of March, the Northeast Monsoon conditions gradually give way to the inter-monsoon conditions, characterised by a gradual increase of rainfall across the northern ASEAN region.
For January 2026, above-normal rainfall is predicted for much of the northeastern and southern Maritime Continent, extending to parts of the northwestern Maritime Continent and southern Mainland Southeast Asia for January – March 2026 overall. La Niña conditions are predicted for January 2026, with a transition to ENSO-neutral predicted in February – March 2026. La Niña events tend to bring wetter conditions to parts of Southeast Asia. Above-normal temperature is predicted for most of the Maritime Continent and western Mainland Southeast Asia for JFM 2026.
While parts of the northern ASEAN region are expected to receive near-normal to above-normal rainfall during the outlook period, hotspot and haze activities remain likely to intensify under the overall dry conditions across the region, with a heightened risk of transboundary smoke haze occurrence. In contrast, the overall hotspot situation across the southern ASEAN region is expected to remain suppressed under the wet weather conditions, though isolated hotspots and localised smoke plumes could develop on occasional days in parts of Borneo where below-normal rainfall is expected. An increase in hotspot activity in the region could occur during the dry phase of the Northeast Monsoon, which typically occurs during late January and February.
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 January 2026, above-normal rainfall is predicted for much of the northeastern and southern Maritime Continent.
For January 2026, above-normal rainfall is predicted over much of the northeastern and southern Maritime Continent based on the multi-model ensemble (Figure 1). Below-normal rainfall is predicted over parts of the central Maritime Continent. For both regions, there is (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, below-normal rainfall is predicted over the northwestern portion (Figure 1) by most models (more than six models, Figure 2). Elsewhere in Mainland Southeast Asia there is little agreement between the models.
Model skill is good for predicting above-normal rainfall over the northeastern Maritime Continent. Model skill is low to moderate for the other regions mentioned.
|
|
| Figure 1: Rainfall tercile summary predictions of the multi model ensemble for January 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for January 2026. Where there 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. 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 JFM 2026, models predict above-normal rainfall over much of the Maritime Continent outside the equatorial region, as well as southern Mainland Southeast Asia.
For JFM 2026, an increase in chance of below-to near-normal rainfall is predicted for much of the equatorial region, with an increase of above-normal rainfall elsewhere in the Maritime Continent, based on the multi-model ensemble (Figure 1). For above-normal rainfall, most models agree for the northeastern part and southern-most part of the region (more than six models) with some models in agreement elsewhere (4 – 6 models, Figure 2). For below-normal rainfall, most models (more than six models) agree for the central equatorial region with little agreement for much of the rest of the equatorial region (less than 4 models).
For Mainland Southeast Asia, an increase in chance of above-normal rainfall is predicted over the southern portion and below-normal rainfall over the northwestern portion, with no dominant tercile elsewhere. Most models (more than 6 models) agree on the region for below-normal, with some models agreeing (4 – 6) for southern Mainland Southeast Asia. Elsewhere in Mainland Southeast Asia no dominant tercile is predicted.
Model skill is good over the northern half of the Maritime Continent for predicting above-normal rainfall, and low to moderate for the southern Maritime Continent. Model skill is low to moderate for below-normal rainfall over northwestern Mainland Southeast Asia and the equatorial region.
|
 |
| Figure 1: Rainfall tercile summary predictions of the multi model ensemble for JFM 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for JFM 2026. Where there 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 JFM based on CHIRPS (reference period: 1991-2020). | Figure 6: Average climatological rainfall’s upper tercile boundary for JFM 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 January 2026, above-normal temperature is predicted over most of the Maritime Continent and northern Mainland Southeast Asia.
For January 2026, above-normal temperature is predicted over most of the Maritime Continent and northern 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 the mentioned regions. Elsewhere, no dominant tercile is predicted (Figure 1). Model skill for predicting above-normal temperature is relatively good for most of the Maritime Continent and low to moderate for Mainland Southeast Asia.
|
|
| Figure 1: Temperature tercile summary predictions of the multi model ensemble for January 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for January 2026. Where there no dominant tercile, it refers to the number of models with near-normal tercile (contains modified Copernicus C3S information). |
|
|
| Figure 5: Average climatological temperature for January 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 JFM 2026, above-normal temperature is predicted over most of the Maritime Continent and western Mainland Southeast Asia.
For JFM 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 most of the Maritime Continent.
For Mainland Southeast Asia, above-normal temperature is predicted over the western portion, with near- to above-normal temperature elsewhere (Figure 1). Most models agree on above-normal temperature as the most likely tercile for western Mainland Southeast Asia, with some models agreeing on the most likely tercile for central and eastern Mainland Southeast Asia (Figure 2). Model skill is generally moderate to good for predicting above-normal temperature for Mainland Southeast Asia and low for predicting near-normal temperature.
|
|
| Figure 1: Temperature tercile summary predictions of the multi model ensemble for JFM 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for JFM 2026. Where there no dominant tercile, it refers to the number of models with near-normal tercile (contains modified Copernicus C3S information). |
|
|
| Figure 5: Average climatological temperature for DJF 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.