Category Archives: Haze Review

Review of Regional Haze Situation for August 2025

1.1 The ASEAN region experienced Southwest Monsoon conditions during August 2025, characterized by prevailing southeasterly or southwesterly winds in the southern ASEAN region and southwesterly or westerly winds in the northern ASEAN region (Figure 1).

1.2 1.2 While Java and the Lesser Sunda Islands continued to face drier conditions, showers were prevalent over the rest of the southern ASEAN region. Alert Level 2 was downgraded to Level 1 for the southern ASEAN region on 12 August 2025 due to the expected improvement of the hotspot and haze situation, and the reduced risk of transboundary haze over the region under the wet weather conditions. In the northern ASEAN region, wet weather continued, particularly over the northern parts of the Philippines and the eastern parts of Mekong sub-region where there was intense rainfall brought by Typhoons Kajiki and Nongfa (Figure 1).

1.3 1.3 The hotspot counts for the ASEAN region in August 2025 were mostly comparable to the same month in previous years (Figures 2 and 3).

1.4 Isolated to scattered hotspots were detected in most parts of the southern ASEAN region, with persistent hotspot clusters detected in West Kalimantan, the northern and central parts of Sumatra, and the Lesser Sunda Islands (Figure 4). Moderate but localised smoke plumes were observed to emanate from hotspots in West Kalimantan and the northern parts of Sumatra on some days (Figures 6 and 7).

1.5 In the northern ASEAN region, the hotspot counts remained low with no significant smoke plumes were observed during the month (Figures 4 and 6).

Review of Regional Haze Situation for July 2025

1.1 Southwest Monsoon conditions persisted over the ASEAN region throughout July 2025. The prevailing winds over the northern ASEAN region blew from the southwest to west. Over the southern ASEAN region, the prevailing winds blew mostly from the southeast to south, except for the winds over the equatorial region which were light and variable in direction (Figure 1).

1.2 Showers were observed over the southern ASEAN region during the first half of July 2025, apart from Java and the Lesser Sunda Islands where it was dry (Figure 1). During the latter half of the review period, dry weather was observed over parts of Kalimantan, Peninsular Malaysia and Sumatra. On 19 July 2025, the Alert Level 2 for the southern ASEAN region was activated due to an escalation of hotspot and smoke haze activities and heightened risk of transboundary smoke haze occurrences in the region. In contrast, the northern ASEAN region experienced wet weather in July 2025, with heavy precipitation recorded over the northern parts of the Philippines due to the influence of Typhoon CO-MAY and Tropical Cyclone WIPHA.

1.3 There was a rise in hotspot activity over the southern ASEAN region due to periods of drier conditions, with hotspot counts higher or comparable to previous years (Figure 2). Notably, Sumatra saw the highest hotspot count over the last 5 years. The hotspot counts for the northern ASEAN region were lower or comparable to the past few years (Figure 3).

1.4 During the latter half of July 2025, there was an increase in hotspot activities in most of the southern ASEAN region, particularly over the western parts of Kalimantan and the central parts of Sumatra where more intense and persistent fires were observed (Figure 4). Slight to moderate smoke plumes were observed over parts of Borneo, Sumatra and Peninsular Malaysia, with transboundary smoke haze observed to drift from the central parts of Sumatra into Peninsular Malaysia and from the western parts of Kalimantan into Sarawak (Figure 6, 7, 8). The hotspot activity over the northern ASEAN region remained subdued under the prevailing wet weather (Figure 4).

Review of Regional Haze Situation for June 2025

1.1 Southwest Monsoon conditions became fully established over the ASEAN region in June 2025. Over much of the southern ASEAN region, the prevailing winds blew mainly from the southeast. The prevailing winds over the Mekong sub-region were mostly southwesterly or westerly while the regions close to the Equator and the Philippines experienced winds that were mostly light and variable in direction (Figure 1).

1.2 Rainy weather prevailed over most parts of the ASEAN region during the review period. In particular, moderate to heavy showers fell on several days over the central parts of Viet Nam under the influence of Typhoon WUTIP. The resulting flooding and landslides were reported across multiple areas in the central parts of Viet Nam . In contrast, drier conditions were observed over Sumatra, Java and the Lesser Sunda Islands (Figure 1). In view of the expected continuation of the dry weather, Alert Level 1 for the southern ASEAN region was activated on 12 June 2025.

1.3 Hotspot activity in the northern ASEAN region was mostly subdued in June 2025 due to the prevailing wet weather conditions. The total number of hotspots were lower or comparable to the same period of previous years (Figure 2). Meanwhile, hotspot counts in the southern ASEAN region were generally comparable to previous years except for Sumatra which recorded the highest number of hotspots in five years (Figure 3).

1.4 In June 2025, a few to isolated hotspots were detected in the ASEAN region, particularly in the northern and central parts of Sumatra, as well as parts of Viet Nam where the fires were more persistent and intense. Slight localised smoke plumes were observed emanating from hotspots in West Kalimantan, Sarawak and the northern and central parts of Sumatra on some days (Figure 4, 5 and Figure 6).

Review of Regional Haze Situation for May 2025

1.1 Inter-monsoon conditions prevailed throughout the ASEAN region during May 2025, characterised by light winds that varied in direction across most parts of the region (Figure 1).

1.2 Wet weather dominated over most parts of the ASEAN region as the monsoon rainband continued to shift northwards from the Equator, with the northern ASEAN region experiencing increased amounts of rainfall compared to previous months. Due to the expected persistent shower activities over the Mekong sub-region, the Alert Level was downgraded from Alert Level 2 to 1 on 13 May 2025, and subsequently from Alert level 1 to 0 on 21 May 2025, signalling the end of the dry season for the sub-region. While showers persisted over most areas in the southern ASEAN region this month, drier conditions were observed over parts of Sumatra and Kalimantan for a few days (Figure 1).

1.3 The hotspot counts for the ASEAN region for May 2025 were comparable to those recorded in May of previous years (Figure 2 & 3).

1.4 Isolated to scattered hotspots were detected over most parts of the Mekong sub-region, especially over the northern parts of Lao PDR where intense and persistent hotspot clusters were observed (Figure 4 and 5). Moderate to dense transboundary smoke haze was also observed to drift eastwards from the northern parts of Lao PDR into the northern parts of Viet Nam on a few days (Figure 6 and 7).

1.5 1.5 Over the southern ASEAN region, the hotspot and smoke haze situation remained mostly subdued. However, there were a few days when slight localized smoke plumes were observed emanating from hotspots in the central parts of Sumatra, the western parts of Kalimantan and Sarawak (Figure 4, 5 and 8).

Review of Regional Haze Situation for April 2025

1.1 During April 2025, the Northeast Monsoon transitioned into the Inter-monsoon conditions as the monsoon band shifted northwards towards the Equator. The period was characterized by the light and variable winds across most of the ASEAN region, except over the Philippines where the prevailing winds blew mostly from the northeast or east (Figure 1).

1.2 Despite increased rainfall over the Mekong sub-region compared to the previous month, drier weather persisted over much of the Mekong sub-region and the northern parts of the Philippines (Figure 1). Given the increased in showers which can improve the hotspot and smoke haze situation, the Alert level for the Mekong sub-region was downgraded to Alert level 2 on 15 April 2025. While showers continued to prevail over the southern ASEAN region, drier conditions were observed over parts of Java towards the end of April 2025 (Figure 1).

1.3 The hotspot counts for the ASEAN region in April 2025 were lower than or comparable to those of previous years (Figure 2, 3).

1.4 Over the Mekong sub-region, scattered to widespread hotspots were detected, especially over the northern parts of the sub-region and the other parts of Lao PDR, where the hotspot clusters were more persistent and intense (Figures 4, 5). Persistent moderate to dense transboundary smoke haze were observed over the northern parts of the Mekong sub-region, as well as the other parts of Lao PDR (Figure 6, 7). In contrast, the southern ASEAN region and the Philippines, experienced low hotspot activity (Figure 6), though slight localised smoke plumes were observed emanating from hotspots detected in the central parts of Sumatra and the eastern parts of Kalimantan (Figure 8).

Review of Regional Haze Situation for March 2025

1.1 During March 2025, the ASEAN region remained under the influence of Northeast Monsoon conditions. Over areas north of the Equator, the surface winds blew predominantly from the northeast or east, apart from the Mekong sub-region where the prevailing winds were generally light and variable in direction. The prevailing low-level winds over areas south of the Equator blew from the west or northwest, while the winds over the equatorial region were light and variable in direction (Figure 1).

1.2 Dry weather persisted over much of the Mekong sub-region and the northern parts of the Philippines (Figure 1). In view of the escalating number of hotspots and the deterioration of the smoke haze situation under the prolonged dry conditions, Alert level 3 for the Mekong sub-region was activated on 17 March 2025, signalling a high risk of severe transboundary haze occurrence. Meanwhile, over the southern ASEAN region, high rainfall was recorded over most parts of the region, especially over the equatorial region, partly due to a Northeast Monsoon surge in the middle of the month (Figure 1), which has led to flooding over parts of Johor, Malaysia. However, drier conditions were also recorded over the northern and central parts of Peninsular Malaysia.

1.3 The hotspot counts for the ASEAN region in March 2025 were generally similar to or lower than those of previous years, except for Myanmar where there was a slight increase from the previous few years (Figure 2, 3).

1.4 Scattered to widespread hotspots were detected in the Mekong sub-region, especially over the northern parts of the Mekong sub-region, as well as the southern parts of Lao PDR and the northeastern parts of Cambodia, where the hotspot clusters were more persistent and intense (Figures 4, 5). Widespread transboundary moderate to dense smoke haze was observed mainly over the northern parts of the Mekong sub-region, as well as the southern parts of Lao PDR and the northeastern parts of Cambodia, where the haze was persistent (Figure 6, 7, 8). Over the southern ASEAN region and the Philippines, the hotspot and smoke haze situation remained subdued (Figure 6).

Review of Regional Haze Situation for February 2025

1.1 Northeast monsoon conditions prevailed throughout February 2025. The prevailing low-level winds generally blew from the northeast or east over areas north of the Equator, except over the Mekong sub-region where the prevailing winds were light and variable in direction (Figure 1). Over areas south of the Equator, the prevailing low-level winds blew from the west or northwest which gradually weakened to become light and variable in direction towards the end of the month.

1.2 Dry conditions continued over most areas of the Mekong sub-region and the northern parts of the Philippines. Relatively drier conditions were also observed over some parts of Peninsular Malaysia under the influence of the dry phase of the Northeast Monsoon. Higher rainfall was recorded over the rest of the ASEAN region, particularly over the southern parts of the Philippines and Sumatra where rainfall was more intense (Figure 1). Flooding and landslides were reported over parts of Indonesia and the Philippines, causing infrastructural damage and displacing people from homes.

1.3 The overall hotspot counts for the ASEAN region in February 2025 were lower than or comparable to those in the same period in previous years (Figures 2 & 3).

1.4 Scattered to widespread hotspots were detected in the northern and central parts of Myanmar, the central parts of Thailand, the southern parts of Lao PDR, and many parts of Cambodia. Isolated to scattered hotspots were detected elsewhere in the northern ASEAN region (Figure 4). Many hotspots detected in the Mekong sub-region were persistent and intense (Figures 4 & 5). This led to the development of moderate to dense smoke haze over the sub-region, particularly over the southern parts of Lao PDR, the northern and central parts of Thailand as well as most parts of Cambodia and Myanmar where the smoke haze was persistent (Figure 6 & 7). Some of this smoke haze became transboundary due to the prevailing wind conditions (Figure 7). Flight disruptions at airports due to smoke haze were reported in Thailand.

1.5 In the southern ASEAN region, the hotspot and smoke haze situation was generally subdued, with a few hotspots detected in parts of Sumatra, Peninsular Malaysia, Kalimantan and Sulawesi on a few days. Occasional slight localised smoke plumes were observed from hotspots detected in Sumatra.

 

 

Figure 4: Distribution of hotspots detected in February 2025 based on NOAA-20 satellite surveillance.

 

Figure 5: Maximum fire intensity in February 2025 based on NOAA-20 satellite surveillance.

 

Figure 6: Number of days with moderate to dense smoke haze observed in February 2025 based on satellite imagery, ground observations, and air quality reports.

 

Figure 7: Transboundary smoke haze over parts of Lao PDR, Cambodia and Viet Nam on 6 February 2025. (Source: NOAA-20 satellite surveillance)

 

Figure 8: Transboundary smoke haze over parts of Lao PDR, and the northern parts of Thailand on 17 February 2025. (Source: NOAA-20 satellite surveillance)

 

Review of Regional Haze Situation for January 2025

1.1 Northeast Monsoon conditions persisted over the ASEAN region in January 2025. During this month, the prevailing low-level winds over regions north of the Equator blew mostly from the northeast or east, except over the northern parts of the Mekong sub-region, where the winds were light and variable in direction. Meanwhile, the prevailing low-level winds over regions south of the Equator blew mainly from the west or northwest (Figure 1).

1.2 As the dry conditions persisted with a gradually increasing number of hotspots since December 2024, Alert Level 1 for the onset of the dry season for the northern ASEAN region was issued on 2 January 2025. Thereafter, under the persisting dry conditions, the hotspot and smoke haze situation over the Mekong sub-region escalated with a heightened risk of transboundary smoke haze occurrence, and Alert Level 2 for the Mekong sub-region was activated on 20 January 2025. Showers were observed elsewhere in the ASEAN region, except for parts of the northern Philippines where there were brief periods of drier weather (Figure 1).

1.3 The overall hotspot counts for the ASEAN region in January 2025 were generally lower than or comparable to hotspot counts recorded for the same period in previous years (Figures 2 and 3).

1.4 Isolated to scattered hotspots were detected in the Mekong sub-region (Figure 4) and the Philippines. Persistent clusters of hotspots, some of which were intense, with moderate to dense smoke plumes were observed consistently in many parts of Cambodia and central Thailand (Figures 4, 6, 7, 8 and 9). Moderate smoke haze was also observed in the northern parts of Thailand, most of Myanmar, as well as the northern and southern parts of Lao PDR (Figures 6, 7 and 8). Towards the end of the month, smoke haze emanating from hotspots detected in the western parts of Cambodia was observed drifting westwards into the central parts of Thailand.

Review of Regional Haze Situation for December 2024

1.1 In December 2024, Northeast monsoon was well established over the ASEAN region as the prevailing low-level winds over most areas north of the Equator blew from the northeast or east except for the northern parts of the Mekong sub-region where the prevailing low-level winds were light and variable in direction. Over the areas south of the Equator, the prevailing low-level winds blew mainly from the west or northwest. (Figure 1).

1.2 Dry conditions were observed over most parts of the Mekong sub-region except for the coastal areas in the southern parts of Viet Nam where showers occurred (Figure 1). Wet weather was observed over rest of the ASEAN region with intense rainfall recorded over southern Thailand and the eastern coastal areas of Peninsular Malaysia (Figure 1). Intense rainfall was also recorded in the eastern parts of the Philippines (Figure 1) under the influence of Tropical Depression Querubin.

1.3 The overall hotspot counts in December 2024 over the ASEAN region were generally lower than or comparable to previous years.

1.4 During the review period, isolated to scattered hotspots were detected in the Mekong sub-region (Figure 4 and 5). While most of the hotspots were short-lived, some were persistent and intense. A few slight localised smoke plumes were also observed to emanate from some hotspots detected in Cambodia, Lao PDR and Thailand (Figure 6). Although a few to isolated hotspots were detected in Sumatra and Kalimantan, the hotspot activities were generally subdued over the southern ASEAN region (Figure 4 and 5).

Review of Regional Haze Situation for November 2024

1.1 Northeast monsoon conditions emerged over the ASEAN region during November 2024 as the prevailing low-level winds over the Mekong sub-region, Peninsular Malaysia, Singapore and the Philippines blew from the northeast or east. Light and variable winds were still observed over areas south of the Equator and the northern parts of the Mekong sub-region (Figure 1).

1.2 Drier conditions were observed over most parts of the Mekong sub-region except for isolated showers recorded over Myanmar and the southern parts of Viet Nam. Showers were observed over most parts of the southern ASEAN region with intense rainfall recorded over southern Thailand and the eastern coastal regions of Peninsular Malaysia where floodings were reported (Figure 1). Intense rainfall was also recorded in the northern parts of the Philippines under the influence of multiple Typhoons and Super Typhoons which led to floodings and landslides in the area.

1.3 The overall hotspot counts in 2024 over the ASEAN region were lower than or comparable to previous years, except for Viet Nam where the hotspot count was slightly higher.

1.4 Persistent isolated hotspots were mostly detected in the central parts of Thailand and Myanmar, as well as the northern and central parts of Viet Nam.