Review of Regional Haze Situation for December 2025
1.1 In December 2025, 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 and 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 some showers were observed (Figure 1). In view of the expected persistence of the dry weather conditions across the sub-region, the Alert Level was activated to Level 1 for the northern ASEAN region, on 26 December 2025, to signal the start of its dry season. Wet weather was observed over the rest of the ASEAN region with intense rainfall recorded over the eastern parts of Peninsular Malaysia (Figure 1). Heavy rainfall was also recorded in the eastern parts of the Philippines (Figure 1) under the influence of Tropical Cyclone WILMA.
1.3 The overall hotspot counts in December 2025 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 (Figures 4 and 5). While most of the hotspots were short-lived, some hotspots in the central parts of Myanmar and Thailand, as well as parts of Cambodia, were persistent and intense. Moderate smoke plumes were observed to emanate from a few hotspots in the southeastern parts of Cambodia and in the southern parts of Viet Nam (Figures 6 and 7). A few slight localised smoke plumes were also observed to emanate from some hotspots detected in the Mekong sub-region. 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).
