Monthly Archives: August 2026

August 27, 2026

Subseasonal Weather Outlook (31 August – 13 September 2026)

Issued: 26 August 2026
First forecast week: 31 August – 6 September 2026
Second forecast week: 7 – 13 Septmeber 2026

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Over much of the southern ASEAN region and parts of southern Mainland Southeast Asia, drier and warmer than usual conditions are predicted in the next fortnight (31 August – 13 September).

Over much of the remaining northern ASEAN region, wetter conditions are predicted in Week 1 (31 August – 6 September).

Most models predict no significant MJO activity during the forecast period (31 August – 13 September).

The outlook is assessed for the region in general, where conditions are relative to the average conditions for the corresponding time of year. For specific updates on the national scale, the relevant ASEAN National Meteorological and Hydrological Services should be consulted.

August 26, 2026

Alert20260826 – Activation of Alert Level 3 for the Southern ASEAN Region

Activation of Alert Level 3 for the Southern ASEAN Region

In recent days, the hotspot and smoke haze situation over the southern ASEAN region has deteriorated further under the prolonged dry conditions. Based on satellite surveillance, widespread moderate to dense smoke haze was observed to emanate from clusters of hotspots detected in Kalimantan, with moderate to dense transboundary haze observed to drift northwards from the hotspot clusters in West Kalimantan. Moderate to dense smoke haze was also observed across large parts of southern and central Sumatra. 287 and 190 hotspots were detected in Kalimantan, and 65 and 81 hotspots were detected in Sumatra, on 24 and 25 August 2026 respectively from the NOAA-20 satellite.

Dry conditions are forecast to persist over most of the southern ASEAN region. Coupled with El Niño conditions that are predicted to strengthen over the coming months, the hotspot and smoke haze situation could escalate further, thereby increasing the risk of severe transboundary haze occurrence in the southern ASEAN region.

August 24, 2026

Review of Regional Weather for July 2026

1. Overview

1.1 During July 2026, a mix of near- to above-average rainfall was recorded over the ASEAN region (Figure 1). Parts of western and eastern Mainland Southeast Asia recorded above-average rainfall while central parts of Mainland Southeast Asia recorded below-average rainfall based on the two datasets (GSMaP-NRT and CMORPH-Blended). Elsewhere, the northwestern Maritime Continent recorded mostly above-average rainfall, with most of the northwestern Maritime Continent and equatorial region recording below-average rainfall. The largest positive (wetter) anomalies were recorded over western Myanmar and southern Malay Peninsula, with the largest negative (drier) anomalies over Sulawesi and the Maluku Islands.

1.2 The observed rainfall anomaly pattern of above-average rainfall over western Mainland Southeast Asia and the below-average rainfall over the southern and eastern Maritime Continent are consistent with the predictions from the subseasonal weather outlooks for July 2026 (6 – 19 July 2026 and 20 July – 2 August 2026). The wet anomalies over western Mainland Southeast Asia and the dry anomalies over the eastern Maritime Continent are consistent with the seasonal outlook for July 2026.

Figure 1: Rainfall anomalies for July 2026 based on GSMaP-NRT data (left) and CPC Global Unified Gauge-based Analysis data (right). The climatological reference period is 2001-2024. Green colour denotes above-average rainfall (wetter), while orange denotes below-average rainfall (drier).

1.3 For Mainland Southeast Asia, below-average temperature was recorded over parts of northern region, with above-average temperature over the southeastern parts and near-average temperature elsewhere (Figure 2). For much of the Maritime Continent, above-average temperature was recorded. The warmest anomalies (1°C – 2°C above average) were recorded over southern Sumatra. The coolest anomalies (-0.25°C – -0.5°C below average) were recorded over parts of northern Lao PDR.

Figure 2: Temperature anomalies for June 2026 based on ERA-5 reanalysis. The climatological reference period is 2001-2024. Red colour denotes above-average temperature (warmer), while blue denotes below-average temperature (colder).

2. Climate Drivers

2.1 The Madden-Julian Oscillation (MJO) was active over the Western Pacific and Western Hemisphere during much of July 2026. In Week 1, an MJO signal was present in the Western Pacific (Phase 7). In Week 2, the MJO signal propagated eastwards to the Western Hemisphere (Phase 8), staying in the Western Hemisphere (Phases 8) in Week 3, before decaying in Week 4 and becoming inactive by the end of the month. Phases 7 and 8 tend to bring drier conditions to much of the ASEAN region. This is somewhat in line with the drier conditions over the eastern Maritime Continent in Figure 1.

Figure 3: The MJO phase diagram. The diagram illustrates the movement of the MJO through different phases, which correspond to different locations along the equator (denoted in the text with the first day of the month in blue and the last day of the month in red). The distance of the index from the centre of the diagram is related to the strength of the MJO. Values within the grey circle are considered weak or indiscernible (data from the Bureau of Meteorology, Australia)..

2.2 The El Niño conditions are now present in July 2026, with the Indian Ocean Dipole (IOD) in the neutral state. El Niño conditions can bring drier conditions to the Maritime Continent at this time of the year.

August 12, 2026

Subseasonal Weather Outlook (17 – 30 August 2026)

Issued: 12 August 2026
First forecast week: 17 – 23 August 2026
Second forecast week: 24 – 30 August 2026

Figure 1: Rainfall Outlook

Figure 2: Temperature Outlook

Over much of the northern ASEAN region, wetter conditions are predicted in Week 1 (17 – 23 August), except over parts of southeastern Mainland Southeast Asia where drier conditions are predicted over the next fortnight (17 – 30 August).

Over much of the southern ASEAN region, drier conditions are predicted in the next fortnight (17 – 30 August).

Warmer than usual temperatures are predicted over much of the ASEAN region in the next fortnight (17 – 30 August), except for most of Mainland Southeast Asia and the southern Maritime Continent.

A Madden-Julian Oscillation (MJO) signal was present over the Western Pacific (Phase 6) towards the middle of August 2026, based on the RMM index. Models predict the MJO signal to remain over the Western Pacific (Phases 6 and 7) during the forecast period (17 – 30 August), with no coherent sign of eastward propagation.

August 5, 2026

Review of Regional Haze Situation for July 2026

1.1 Southwest Monsoon conditions continued over the ASEAN region throughout July 2026. The prevailing winds across the southern ASEAN region blew mainly from the southeast to south, while winds over the northern ASEAN region blew mostly from the southwest to west (Figure 1).

1.2 Showers were observed over many parts of the ASEAN region during the review period, except over Java and the Lesser Sunda Islands, where persistent dry conditions were observed (Figure 1). The southern parts of Sumatra, and the southern and central parts of Borneo also experienced periods of dry weather. On 10 July 2026, the Alert Level 1 for the southern ASEAN region was activated, signalling the start of the dry season. Over the northern ASEAN region, relatively higher rainfall was recorded over the northern parts of Viet Nam and the Philippines due to Typhoon Maysak, Bavi and Noul.

Figure 1: Average Daily Rainfall and Mean Winds for July 2026. (Source: JAXA GsMaP and GFS, respectively)

1.3 The hotspot counts for July 2026 over the ASEAN region were generally comparable to previous years (Figure 2 and 3), except in Cambodia, where hotspot counts were slightly higher relative to the past four years (Figure 3).

Figure 2: Hotspot counts for the southern ASEAN region for July (2022-2026) based on NOAA-20 satellite surveillance.

Figure 3: Hotspot counts for the northern ASEAN region for July (2022-2026) based on NOAA-20 satellite surveillance.

1.4 Hotspot activities were more persistent in West Kalimantan and parts of the Lesser Sunda Islands towards the latter half of the review period (Figure 4), with more intense fires detected in West Kalimantan as well (Figure 5). Slight to moderate smoke plumes were observed mainly over Java, parts of Borneo, and the northern and southern parts of Sumatra, with transboundary smoke haze observed to drift from West Kalimantan into the western parts of Sarawak on a few days (Figures 6 – 10). Slight to moderate smoke plumes were also observed over the central parts of Cambodia and Viet Nam on a few days.

Figure 4: Distribution of hotspots detected in July 2026 based on NOAA-20 satellite surveillance.

Figure 5: Maximum fire intensity in July 2026 based on NOAA-20 satellite surveillance.

Figure 6: Number of days with moderate to dense smoke haze observed in July 2026 based on satellite imagery, ground observations, and air quality reports.

Figure 7: Moderate localised smoke plume observed over the northern parts of Sumatra on 8 July 2026. (Source: Himawari-9 satellite surveillance)

Figure 8: Moderate smoke plumes observed over West Kalimantan drifting in the northwest direction into the western part of Sarawak on 15 July 2026. (Source: Himawari-9 satellite surveillance)

Figure 9: Slight to moderate localised smoke plumes observed over the eastern parts of Java on 17 July 2026. (Source: Himawari-9 satellite surveillance)

Figure 10: Moderate localised smoke plumes observed over Central and South Kalimantan on 26 July 2026. (Source: Himawari-9 satellite surveillance)

August 3, 2026

Alert20260803 – Activation of Alert Level 2 for the Southern ASEAN Region

Activation of Alert Level 2 for the Southern ASEAN Region

In recent days, prevailing dry weather conditions over the southern ASEAN region have resulted in an escalation in hotspot and smoke haze activities. Based on satellite surveillance, moderate smoke haze was observed to emanate from clusters of hotspots detected in the western and southern parts of Kalimantan. A few smoke plumes were also observed from hotspots detected in the southern parts of Sumatra. 185 and 371 hotspots were detected in Kalimantan, and 26 and 11 hotspots were detected in Sumatra, on 1 and 2 August 2026 respectively from the NOAA-20 satellite.

The hotspot and smoke haze situation over the region is expected to deteriorate as dry weather is expected to persist across the southern ASEAN region, coupled with El Niño conditions that are predicted to continue strengthening over the coming months. This could increase the risk of transboundary haze over the region.