Seasonal Forecast for April – June 2026
Updated 07 April 2026
Inter-monsoon conditions are currently prevailing over most of the region. During the inter-monsoon period, prevailing winds are generally light and variable in direction. Over the Mekong sub-region, the traditional dry season usually extends into the inter-monsoon period, although there can be occasional showers. The southern ASEAN region typically experience showers, interspersed with periods of drier conditions. Following the inter-monsoon period, the Southwest Monsoon usually set in from May to the beginning of June, with winds turning to blow from the southeast or southwest. The traditional dry season for the southern ASEAN region is expected to set in around this time.
For April 2026, below-normal rainfall is predicted for most of the southern ASEAN region. Below-normal rainfall is also predicted for April – June 2026. La Niña conditions are predicted to continue weakening and transition to ENSO-neutral conditions in March – April 2026. ENSO-neutral conditions are predicted for May 2026, with either ENSO-neutral continuing or El Niño conditions developing in June-July 2026. Above-normal temperature is predicted for most of the ASEAN region for AMJ 2026.
The hotspot and smoke haze situation is expected to remain elevated over the Mekong sub-region under the persistent dry conditions, with continued risk of transboundary haze occurrence. The situation would gradually improve when the showers return around the end of April or the start of May 2026. For the first three months of 2026, hotspot counts over the southern ASEAN region have been higher than during the same period in 2025. Smoke plumes were observed from hotspots in the region on several occasions. With below-normal rainfall expected over most parts of the southern ASEAN region for the period of April – June, hotspot and smoke plumes could continue to develop, and there could be some risk of haze, particularly in areas where below-normal rainfall is predicted. The risk of haze could increase as the region progresses into its traditional dry season when the Southwest Monsoon sets in around end May.
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 April 2026, below-normal rainfall is predicted over most of the southern ASEAN region, while near-normal or no dominant tercile is predicted for the northern ASEAN region.
For April 2026, below-normal rainfall is predicted over most of the southern ASEAN region, based on the multi-model ensemble (Figure 1). For the southernmost part of this region, most of the models (more than six models, Figure 2) predict below-normal rainfall as the dominant tercile, while four to six models agree on below-normal rainfall over much of the equatorial region. Model skill is low to moderate for below-normal rainfall over the southern ASEAN region.
For northern ASEAN region, four to six models agree on the near-normal rainfall predicted over southern Mainland Southeast Asia and southern half of the Philippines, with no dominant tercile being predicted elsewhere (little agreement between the models). 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 April 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for April 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 April based on CHIRPS (reference period: 1991-2020). | Figure 6: Average climatological rainfall’s upper tercile boundary for April 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.
FFor AMJ 2026, below-normal rainfall for the southern ASEAN region.
For AMJ 2026, an increased chance of below-normal rainfall is predicted for the southern ASEAN region, , based on the multi-model ensemble (Figure 1). Most models (more than six models) agree for the region of higher confidence in below-normal rainfall, with some models (4 – 6 models) predicting below-normal rainfall for the rest of the region. Model skill is low to moderate over the southern ASEAN region at this time of year.
For the northern ASEAN region, no dominant tercile is predicted for much of the region, apart from some models (4 – 6 models) in agreement regarding an increase in chance of above-normal rainfall predicted over much of the northeastern part. Model skill is good over the northeastern region for predicting above-normal rainfall, and low for the rest of the region.
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| Figure 1: Rainfall tercile summary predictions of the multi model ensemble for AMJ 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for AMJ 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 AMJ based on CHIRPS (reference period: 1991-2020). | Figure 6: Average climatological rainfall’s upper tercile boundary for AMJ 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 April 2026, above-normal temperature is predicted over the southern ASEAN region and near- to above-normal temperature over the northern ASEAN region.
For April 2026, above-normal temperature is predicted over most of the southern ASEAN region, with the highest likelihood over the eastern part, 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 southern ASEAN region. For the northern ASEAN region, a mix of near-normal and near- to above-normal temperature is predicted, with some models (4 to 6) in agreement regarding the most likely tercile. Model skill for predicting above-normal temperature is relatively good for the southern ASEAN region, and moderate to good for the northern ASEAN region.
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| Figure 1: Temperature tercile summary predictions of the multi model ensemble for April 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for April 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 April 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 AMJ 2026, above-normal temperature is predicted over most of the ASEAN region.
For AMJ 2026, above-normal temperature is predicted over most of the ASEAN region (Figure 1). For the southern ASEAN region most models (more than six models) predict above-normal temperature as the most likely tercile over this region (Figure 2). For the northern ASEAN region, most models agree on above-normal temperature as the most likely tercile for the southernmost and northernmost regions, with some models (4 to 6 models) agreeing on the most likely tercile elsewhere (Figure 2). Model skill for predicting above-normal temperature is good for the southern ASEAN region and moderate to good for predicting above-normal temperature for the northern ASEAN region.
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| Figure 1: Temperature tercile summary predictions of the multi model ensemble for AMJ 2026 (contains modified Copernicus C3S information). | Figure 2: Number of models in agreement in the multi-model ensemble for the dominant tercile for AMJ 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 AMJ 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.