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Southeast Asian haze history: every major episode since 1997, with the numbers

Updated · Every figure links to its source below.

The worst haze years were 1997–98, 2013, 2015 and 2019. Singapore's highest reading is a 3-hour PSI of 401 on 21 June 2013. The 2015 haze was the costliest: the World Bank put Indonesia's losses at US$16.1 billion, and one study estimated 100,300 excess deaths in Indonesia, Malaysia and Singapore. In 2026 Singapore's 24-hour PSI has reached 192 (9 October).

Key facts

  • Singapore's record: 3-hour PSI 401 at noon on 21 June 2013; the highest 24-hour PSI on record is 246, on 22 June 2013.
  • Malaysia's highest widely reported reading: API 746 in Muar, Johor, at 7am on 23 June 2013.
  • 2015: about 2.6 million hectares burned in Indonesia, costing an estimated US$16.1 billion (1.9% of GDP), per the World Bank.
  • 2015: an estimated 100,300 excess deaths (Indonesia 91,600, Malaysia 6,500, Singapore 2,200), per Koplitz et al., Environmental Research Letters, 2016.
  • 25 September 2015 was the first time all of Singapore's primary and secondary schools closed because of haze.
  • 2019: Indonesia's environment ministry recorded 1,649,258 hectares burned; the World Bank estimated losses of at least US$5.2 billion.
  • 2026: ASMC raised the southern ASEAN haze alert to Level 3 on 26 August; Singapore's 24-hour PSI peaked at 192 (central) on 9 October, as of 13 October.
Singapore now · loading the official reading…

Timeline at a glance

Major haze episodes affecting Singapore and Malaysia
YearSingapore peakMalaysiaScale and cost
19973-hour PSI 226 (18 Sep), the record until 2013Kuching API about 839 (23 Sep); state of emergency in Sarawak, 19–28 SepAbout 9.7 million ha burned; haze damage about US$4.5 billion (Aug–Dec 1997, EEPSEA/WWF)
2006PSI 128 (7 Oct)——
20133-hour PSI 401 (21 Jun, all-time record); 24-hour PSI 246 (22 Jun)Muar API 746 (23 Jun); emergency in Muar and LedangA short, extreme June episode
20153-hour PSI 341 (25 Sep); all schools closed that day4,778 schools (2.7 million students) closed on 22 Oct2.6 million ha burned; US$16.1 billion (World Bank); about 100,300 excess deaths (Koplitz et al.)
201924-hour PSI Unhealthy from 14 Sep; 111–131 on 18 Sep2,459 schools (1.7 million students) closed on 19 Sep1.65 million ha burned (KLHK); at least US$5.2 billion (World Bank)
202324-hour PSI up to 120 (7 Oct), first Unhealthy reading since 2019—Two days in the Unhealthy range (7–8 Oct)
202624-hour PSI 192, central (9 Oct), highest so farEmergency in Serian, Sarawak (API 518–521, 4 Sep); schools close above API 180 from 8 OctASMC Alert Level 3 from 26 Aug; season still under way

Readings before 2016 often quote the 3-hour PSI, which NEA no longer publishes; before April 2014 the PSI did not include PM2.5. Compare like with like.

1997–98: the regional disaster

A strong El Niño left Indonesia unusually dry, and fires set to clear land spread into forest and peat. About 9.7 million hectares burned across Indonesia in 1997–98 (ADB and BAPPENAS; a later CIFOR estimate is 11.7 million). Singapore's 3-hour PSI reached 226 at 10pm on 18 September 1997, a record that stood until 2013.

Sarawak was hit hardest: Kuching's API passed 800 (about 839 on 23 September), and a state of emergency ran from 19 to 28 September 1997. An EEPSEA/WWF study put the haze damage from August to December 1997 at about US$4.5 billion; the ADB's estimate for 1997–98 as a whole exceeds US$9 billion.

2006: a strong haze in a dry year

Fires in Sumatra and Kalimantan during a dry El Niño year brought several weeks of haze in September and October. Singapore's PSI peaked at 128 on 7 October 2006 (National Library Board).

2013: Singapore's record reading

In mid-June 2013, fires in Riau, central Sumatra, met south-westerly winds blowing straight towards Singapore and southern Johor. Singapore's 3-hour PSI hit 401 at noon on 21 June, the highest PSI ever recorded there, and the 24-hour PSI reached 246 on 22 June, still the highest on record.

Across the strait, Muar in Johor recorded an API of 746 at 7am on 23 June, and Malaysia declared an emergency in Muar and Ledang the same day.

2014–2016: the rules change

  • 1 April 2014: NEA added PM2.5 to the PSI as its sixth pollutant and began publishing hourly PM2.5 readings.
  • 5 August 2014: Singapore passed the Transboundary Haze Pollution Act, in force from 25 September 2014.
  • 16 September 2014: Indonesia's parliament approved ratification of the 2002 ASEAN Agreement on Transboundary Haze Pollution, the last member state to do so.
  • 2016: NEA phased out the 3-hour PSI and introduced the four 1-hour PM2.5 bands (Normal, Elevated, High, Very High) used today.

2015: the costliest haze

Another strong El Niño dried out Sumatra and Kalimantan, and drained peatland burned for months. The World Bank counted 2.6 million hectares burned between June and October and estimated the cost to Indonesia at US$16.1 billion, 1.9% of GDP. A Harvard- and Columbia-led study (Koplitz et al., 2016) estimated 100,300 excess deaths: 91,600 in Indonesia, 6,500 in Malaysia and 2,200 in Singapore.

Singapore's highest reading was a 3-hour PSI of 341 at 5am on 25 September; with the 24-hour PSI forecast to reach Very Unhealthy or Hazardous, all primary and secondary schools closed that day, a first. Malaysia closed schools repeatedly: 2,045 on 15 September and 4,778, with 2.7 million students, on 22 October.

2019: a dry year without a strong El Niño

A strong positive Indian Ocean Dipole kept western Indonesia dry. Indonesia's environment ministry recorded 1,649,258 hectares burned, and the World Bank estimated losses of at least US$5.2 billion (0.5% of GDP). Singapore's 24-hour PSI entered the Unhealthy range on 14 September, and NEA's 18 September update showed 111–131. Malaysia closed 2,459 schools, affecting 1.7 million students, on 19 September.

2023: a brief return

On 7 October 2023 Singapore's 24-hour PSI went above 100 for the first time since 2019, reaching 120, and fell back after 8 October.

2026: the season so far

  • 10 July: ASMC Alert Level 1 for the southern ASEAN region; Level 2 on 3 August; Level 3 (high risk of severe haze) on 26 August.
  • 4 September: Singapore's 24-hour PSI reached 101 (central), its first Unhealthy reading since October 2023. The same day Malaysia declared an emergency in Serian, Sarawak, where the API passed 500; 647 Sarawak schools closed from 7 to 11 September.
  • 15 September: the whole of Singapore was in the Unhealthy range for the first time since 2019 (central 154).
  • 8 October: Malaysia's Education Ministry ordered schools to close where the API is above 180, or above 150 for three days in a row; Segamat (190), Seremban (189) and Nilai (183) were above 180 that evening.
  • 9 October: Singapore's 24-hour PSI reached 192 (central), the season's highest so far; on 12 October at 7pm it was 118–155.

What the bad years have in common

  • A dry season made drier by El Niño (1997, 2006, 2015) or a positive Indian Ocean Dipole (2019).
  • Burning in drained peatland, which smoulders for weeks and produces dense smoke.
  • Winds from the south-east or south-west between about August and October that carry smoke from Sumatra and Kalimantan to Singapore and Malaysia.

Quick answers

What was the worst haze in Singapore's history?

By peak reading, June 2013: the 3-hour PSI hit 401 on 21 June and the 24-hour PSI 246 on 22 June. By duration and harm, 2015: weeks of Unhealthy air, the first island-wide school closure on 25 September, and an estimated 2,200 excess deaths in Singapore.

How much did the 2015 haze cost?

The World Bank estimated the 2015 fires cost Indonesia US$16.1 billion, about 1.9% of GDP, from about 2.6 million hectares burned between June and October.

Is the 2026 haze as bad as 2015?

Not by Singapore's readings so far. As of 13 October 2026 the 24-hour PSI has peaked at 192, in the Unhealthy range; in 2015 it went into the Very Unhealthy and Hazardous ranges. Parts of Malaysia, such as Serian in Sarawak, have seen far higher API readings.

Related questions

More reference pages

References

  1. Haze (Infopedia). National Library Board, Singapore.
  2. Smoke engulfs Singapore. NASA Earth Observatory, 2013.
  3. Haze and dengue: the unanswered questions. Annals, Academy of Medicine, Singapore.
  4. Haze: API in Muar spikes at 746. The Star, 2013.
  5. The cost of the 1997 haze and fires in Indonesia (EEPSEA/WWF). Economy and Environment Program for Southeast Asia, 1998.
  6. The cost of fire: an economic analysis of Indonesia's 2015 fire crisis. World Bank, 2016.
  7. Public health impacts of the severe haze in Equatorial Asia in September–October 2015 (Koplitz et al.). Environmental Research Letters, 2016.
  8. Singapore schools close for the first time due to haze. The Star, 2015.
  9. Schools to close for fourth day as haze causes very unhealthy pollution levels. Malay Mail, 2015.
  10. New bands for one-hour PM2.5 readings in Singapore. Malay Mail, 2016.
  11. RI ratifies haze treaty. The Jakarta Post, 2014.
  12. Transboundary Haze Pollution Act 2014. Singapore Statutes Online, 2014.
  13. Indonesia's fires cost the nation $5 billion this year: World Bank. Mongabay, 2019.
  14. Haze situation update, 18 September 2019. National Environment Agency, 2019.
  15. Haze situation update, 7 October 2023. National Environment Agency, 2023.
  16. Activation of Alert Level 3 for the southern ASEAN region. ASEAN Specialised Meteorological Centre, 2026.
  17. Singapore records first islandwide unhealthy PSI since 2019 as haze worsens. Malay Mail, 2026.
  18. King consents to emergency declaration in Serian. New Straits Times, 2026.
  19. Jerebu: sekolah ditutup mulai esok jika IPU lebih 180 (KPM). Portal Berita RTM, 2026.
  20. Haze situation update, 9 October 2026. National Environment Agency, 2026.

Sources

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