Haze Day When is haze season? A month-by-month calendar for Southeast Asia
Updated · Every figure links to its source below.
For Singapore, Malaysia and Indonesia, haze season usually runs from about June to October, during the Southwest Monsoon, and is worst from August to October, when fires in Sumatra and Kalimantan peak and winds carry the smoke north. Rains from November usually end it. Northern ASEAN (Thailand, Laos, Myanmar) has a separate season from about January to April.
Key facts
- Southern ASEAN haze season: roughly June to October, peaking August to October.
- Northern ASEAN haze season: roughly January to April, from dry-season burning in the Mekong region.
- ASMC issues four alert levels (0–3); Level 3 means a high risk of severe transboundary haze.
- June 2013 is the notable exception: Singapore's record PSI of 401 came early in the season.
Month by month
| Months | Singapore, Malaysia, Indonesia (southern ASEAN) | Thailand, Laos, Myanmar (northern ASEAN) |
|---|---|---|
| Jan–Apr | Usually low. Northeast Monsoon rain; short dry spells can bring isolated hotspots. | Haze season: dry-season burning, usually worst around February to April. |
| May | Usually low | Rains begin and the haze usually ends. |
| Jun–Jul | Southwest Monsoon sets in; the dry season starts in Sumatra and Kalimantan and hotspots begin to rise. ASMC often moves to Alert Level 1. | Usually low |
| Aug–Oct | Peak season. Most hotspots, driest peat, and south-easterly or south-westerly winds towards Singapore and Malaysia. Most severe episodes fall here. | Usually low |
| Nov–Dec | Inter-monsoon showers, then the Northeast Monsoon; rain usually ends the haze and ASMC stands down. | Dry season starts; burning builds from December. |
In dry El Niño or positive Indian Ocean Dipole years the southern season tends to start earlier, last longer and be more severe.
ASMC haze alert levels
The ASEAN Specialised Meteorological Centre (ASMC) sets an alert level separately for the southern and the northern ASEAN regions. The level describes regional fire and smoke risk; it is not a local air-quality reading.
| Level | Meaning | Typical trigger |
|---|---|---|
| 0 | No transboundary haze risk | Wet season; alert stood down |
| 1 | Dry season has started | Onset of the dry season in the region |
| 2 | Increasing risk of transboundary haze | Escalating hotspots with moderate to dense smoke for 2 or more days, dry weather persisting, winds blowing smoke towards neighbouring countries |
| 3 | High risk of severe transboundary haze | Significant, persistent hotspots with widespread moderate to dense smoke for 2 or more days, under the same dry, windy conditions |
2026 so far
ASMC raised the southern ASEAN region to Alert Level 1 on 10 July 2026, Level 2 on 3 August and Level 3 on 26 August. Singapore's 24-hour PSI first entered the Unhealthy range on 4 September and reached 192 on 9 October. For the live picture, see the haze season tracker; for earlier years, see the haze history.
Quick answers
When does haze season end in Singapore?
Usually in late October or November, when inter-monsoon showers and then the Northeast Monsoon bring steady rain over the fire areas and change the wind direction. In dry years it can drag into November.
What does ASMC Alert Level 3 mean?
It is the highest level: a high risk of severe transboundary haze, declared when significant, persistent hotspots and widespread moderate to dense smoke last two or more days while dry weather and winds keep carrying smoke across borders.
Related questions
More reference pages
References
- ASMC alerts and alert level definitions. ASEAN Specialised Meteorological Centre.
- Activation of Alert Level 2 for the southern ASEAN region. ASEAN Specialised Meteorological Centre, 2026.
- Activation of Alert Level 3 for the southern ASEAN region. ASEAN Specialised Meteorological Centre, 2026.
- Haze (Infopedia). National Library Board, Singapore.
- Haze severity depends on hotspots, winds and atmospheric mixing. NUS College of Design and Engineering, 2026.
- Haze situation update, 9 October 2026. National Environment Agency, 2026.
Sources
- ASEAN Specialised Meteorological Centre (ASMC) — ASEAN Specialised Meteorological Centre, hosted by the Meteorological Service Singapore · official site
- haze.gov.sg regional haze situation and outlook — NEA, drawing on the ASEAN Specialised Meteorological Centre · official site
- NASA FIRMS active-fire detections (VIIRS) — NASA Fire Information for Resource Management System (FIRMS) · official site · API / docs
Cite this page
Haze Day. “When is haze season? A month-by-month calendar for Southeast Asia.” haze.day, updated . https://haze.day/en/learn/haze-season-calendar
Licensed CC BY 4.0: free to quote and reuse with credit and a link. HTML link:
<a href="https://haze.day/en/learn/haze-season-calendar">When is haze season? A month-by-month calendar for Southeast Asia</a> (Haze Day)