Last Updated on October 18, 2026 by Jeff Tomas
When Singapore’s skies turn gray, the smoke often comes from fires beyond its borders, carried across the region by changing winds. The haze raises immediate questions: where the fires are burning, why the smoke reaches the island, and what breathing it means for your health and daily routine.
Dry weather can make fires harder to control, while monsoon winds help determine whether smoke reaches Singapore. The effects vary by person and episode, so historical haze events and current health guidance offer useful context. Here’s how the causes, risks, and practical precautions fit together, including the health effects of Singapore’s toxic haze.
Key Takeaways
- Singapore’s haze often comes from fires in Sumatra or Kalimantan, with winds carrying smoke across the region.
- Dry weather raises fire risk, while burning peat can smolder underground and keep releasing smoke.
- Fine particles called PM2.5 can reach deep into the lungs, and haze may worsen respiratory symptoms.
- Check NEA’s 24-hour PSI forecast and health guidance to adjust outdoor activity during haze.
- Children, older adults, pregnant women, and people with heart or lung conditions face greater concern; review health risks of Singapore’s toxic haze.
The Main Causes and Effects of Haze in Singapore
Singapore’s haze usually begins with fires in Indonesia, especially in Sumatra and Kalimantan. Smoke and fine particles can travel across the region on prevailing winds, reducing air quality in Singapore. Unlike ordinary mist, which consists mainly of tiny water droplets, haze contains airborne pollution from smoke.
How land clearing and peat fires create smoke
Some fires are deliberately set to clear vegetation for farming or plantations. However, not every fire is intentional. Dry weather can allow accidental ignitions to spread, and the location and scale of fires help determine how much smoke reaches Singapore.
Peatlands can make fires especially hard to control. Peat is partly decomposed plant material beneath the ground. When it dries out and catches fire, it can smolder underground, where flames are difficult to spot and reach. As a result, a fire may keep burning and releasing smoke long after surface flames appear to be out.
Winds then carry smoke across borders, while rainfall can help dampen fires. That means haze severity depends not only on fires themselves, but also on how dry conditions are and which way the winds blow.
Why fine particles are a health concern
Smoke haze contains PM2.5, a term for airborne particles no larger than 2.5 micrometers. These particles are small enough to travel deep into the lungs when inhaled. Exposure can irritate the airways and aggravate conditions such as asthma. Read more about PM2.5 exposure and health risks.
Singapore reports air quality through the Pollutant Standards Index, or PSI. The index combines readings for several pollutants, including PM2.5, which the National Environment Agency added to the 24-hour PSI calculation in April 2014. The NEA’s explanation of the PSI clarifies how the index is calculated.
PSI and PM2.5 readings are related, but they are not interchangeable. PSI combines multiple pollutants into one index, while a PM2.5 reading measures the concentration of those fine particles. During haze, checking both can give a clearer picture of conditions and help you follow the appropriate health advice.
How Dry Weather and Monsoon Winds Bring Haze to Singapore
Haze reaches Singapore when fires produce enough smoke, dry conditions allow them to persist, and winds carry the smoke toward the island. Fires elsewhere in Indonesia do not automatically mean Singapore will experience poor air quality. Rainfall and wind direction can change the outcome.
Why the Southwest Monsoon raises haze risk
Singapore faces a higher risk of transboundary haze during the Southwest Monsoon months. Winds can carry smoke from Sumatra and other parts of Indonesia toward Singapore, but the plume’s route depends on conditions at the time.
The June 2013 episode shows how quickly smoke can affect the island. Fires in Sumatra sent smoke toward Singapore as prevailing winds came from the southwest or west. NASA’s satellite imagery captured smoke from Sumatra over Singapore and southern Malaysia during the episode. The event also shows that a serious haze episode does not require El Niño: research on the June 2013 haze found it occurred without El Niño conditions.
Even when fires burn nearby, wind direction matters. If winds carry smoke away from Singapore, the island may avoid the worst of the plume. If they blow toward Singapore, haze can arrive and worsen when fires continue to release smoke.
How drought, El Niño, and rain change the outlook
Drought dries vegetation and peat, making them easier to ignite. It can also make fires harder to control, especially when peat burns below the surface and continues smoldering. As fires spread or persist, they can release smoke over a longer period.
El Niño can intensify drought in the region and increase fire risk, but it is not a requirement for severe haze. The June 2013 episode occurred without El Niño, while drought linked to El Niño worsened the 2015 fires. El Niño’s effects on Indonesia’s peatlands help explain why some fire seasons become more severe.
Rain can dampen vegetation and peat, helping reduce fire activity and smoke emissions. However, seasonal patterns vary, and rainfall may not reach affected areas at the same time. Singapore’s air quality depends on the combination of where and how intensely fires burn, how dry the land becomes, whether rain reaches fire zones, and which direction the winds carry smoke.
What Past Haze Episodes Reveal About Their Severity
Singapore’s history shows that haze can arrive quickly, peak at very different levels, or persist for weeks. PSI readings also use different averaging periods, so a short-term peak should not be compared directly with a 24-hour value.
The 1997 and 2013 episodes
In 1997, smoke from fires in Indonesia created one of Singapore’s first major haze emergencies. The reported peak was a 3-hour average PSI of 226 on September 18. That reading captures a short period of very poor air quality, rather than a full day’s average.
The June 2013 episode began affecting Singapore on June 13, as smoke from fires in Sumatra moved across the region. On June 21, the 3-hour average PSI reached 401, a far higher short-term peak than in 1997. Keep the averaging period in mind when comparing these figures: both are 3-hour readings, but neither describes conditions across an entire day. The 2013 peak also shows how sharply air quality can deteriorate when smoke and weather conditions combine.
The prolonged haze of 2015
The 2015 episode lasted much longer. Fires in Sumatra and Kalimantan, alongside drought conditions linked to El Niño, fueled haze from mid-September through October. A National University of Singapore account of the 2015 haze describes the episode as lasting about nine weeks. Unlike a brief spike, prolonged exposure can keep disrupting daily life even when air quality fluctuates.
During the episode, the 24-hour PSI reached 322. That figure represents a full-day average, so it cannot be compared directly with the 3-hour peaks from 1997 or 2013. A study of Singapore’s 2015 haze estimated economic costs at S$700 million and estimated 2,200 excess deaths in the following year. Those are study findings, not settled official counts or proof that each death resulted from haze exposure. Separately, scrutiny of the causes has included reports on palm oil firms and Singapore haze.
Together, these episodes show why severity depends on more than a single PSI peak. The 2013 event set a higher 3-hour peak, while the 2015 haze combined a high 24-hour reading with a prolonged period of exposure.
How Haze Affects Health, Work, and Daily Life
Haze can affect people differently, depending on their health, the pollution level, and how long they spend outdoors. Some experience mild irritation, while others need to take stronger precautions. Its effects can also reach beyond health, changing school plans, outdoor routines, and work schedules.
Common symptoms and higher-risk groups
Short-term exposure may cause a runny nose, sore throat, sneezing, or irritated eyes. Smoke particles can also trigger coughing and worsen asthma or other breathing problems. Symptoms may ease when exposure drops, but people with ongoing or worsening breathing trouble should seek medical advice.
Children, older adults, pregnant people, and those with heart or lung conditions may need extra care. Children’s lungs are still developing, while older adults and people with chronic conditions may have less reserve to cope with poor air quality. The Singapore Ministry of Health explains how haze can affect heart and lung health. Parents can also review how poor air quality affects children.
Risk isn’t identical for everyone, so follow Singapore’s current health advisory rather than relying on a single reading or assuming everyone will react the same way.
Disruptions beyond the health effects
When haze worsens, people may need to limit strenuous outdoor activity, reschedule sports, or move events indoors. Schools may adjust activities or, in severe conditions, close. On September 25, 2015, Singapore closed its primary and secondary schools because of the haze. That decision reflected the conditions during that episode, not a standard response to every haze event.
Work can also become harder to manage when employees commute outdoors, work outside, or develop symptoms. Employers may need to adjust outdoor duties, while families arrange care when school plans change. Clinics and emergency departments can face added demand as people seek help for breathing or irritation symptoms. A study of Southeast Asian haze episodes documents acute health impacts linked to transboundary haze, but reported effects from one episode should not be treated as a forecast for every year.
These disruptions vary with haze severity and duration. Checking current air-quality guidance helps individuals, schools, and workplaces decide when to reduce outdoor exposure.
How Singaporeans Can Respond and Why Regional Action Matters
Singaporeans can reduce exposure during a haze episode by following current health advice and adjusting outdoor plans. However, personal precautions address only immediate risk. Long-term prevention also depends on reducing fires in the places where they start.
How to use PSI, PM2.5, and health advice
A 3-hour PSI reading offers a short-term snapshot, so it can change quickly. Singapore’s health advisories instead use 24-hour PSI and 24-hour PM2.5 readings. The guidance follows whichever measure indicates greater concern, as explained in the Ministry of Health’s haze guidance.
Check the National Environment Agency’s current haze updates and follow the advice for your risk group. Healthy adults, children, older adults, pregnant women, and people with heart or lung conditions may receive different recommendations. A brief PSI spike is useful context, but it does not replace the 24-hour health advisory.
Steps to reduce exposure during a haze episode
When the advisory recommends it, limit prolonged or strenuous outdoor activity. Consider moving exercise indoors, shortening outdoor errands, or postponing demanding activities until conditions improve. Keep checking updates, since readings and guidance can change during the day.
Higher-risk groups should take a more cautious approach and follow the specific recommendations for them. People with chronic heart or lung conditions may need to avoid outdoor exertion at levels where healthy adults are advised only to reduce it. If you feel seriously unwell, seek medical care rather than trying to diagnose the cause yourself.
Why preventing fires requires regional cooperation
Haze crosses national borders, so Singapore’s preparedness cannot prevent smoke from reaching the island on its own. Lasting progress depends on reducing land fires in fire-prone areas, improving peatland management, and sharing timely information about fires and smoke. Countries also need effective firefighting support and enforcement of rules against illegal burning.
The ASEAN Agreement on Transboundary Haze Pollution provides a regional framework for cooperation. It does not mean the problem has ended; preventing fires requires continued work where they occur, alongside readiness in downwind countries. Recent regional discussions have also highlighted ASEAN cooperation on cross-border haze, including shared monitoring and early warning. For Singapore, personal precautions and regional prevention address different parts of the same problem.
Frequently Asked Questions
The questions below address details that can help you interpret haze conditions and decide which updates to follow. The key is to distinguish regional fire activity from the air quality Singapore actually experiences.
Does every fire in Indonesia cause haze in Singapore?
No. The effect depends on the fire’s location and size, how much smoke it produces, and whether winds carry that smoke toward Singapore. Weather also matters: rainfall can limit fire activity, while dry conditions can keep fires burning. Smoke from Indonesia can affect other parts of the region, too, as seen in reports of transboundary haze from Indonesia.
When is haze most likely to affect Singapore?
The risk is higher during the Southwest Monsoon season, when regional wind patterns can carry smoke toward Singapore. However, the season doesn’t guarantee haze, and a haze episode doesn’t begin on the same date every year. Its timing and severity depend on fire activity, rainfall, and winds during that particular year.
What is the difference between PSI and PM2.5?
The PSI is a combined air-quality index that takes several pollutants into account; PM2.5 is one pollutant it measures. A PM2.5 reading describes the concentration of fine particles in the air, while PSI turns several pollutant readings into an index. Singapore reports both because they provide different information about air quality and possible health concerns.
Can rain clear the haze?
Rain can wash some particles from the air and dampen vegetation, which may slow or reduce fires. Its effect depends on where the rain falls and how much reaches the affected fire areas. If fires continue or rainfall misses those areas, smoke can persist or return. Rain in Singapore alone may not put out fires elsewhere.
Is a short-term PSI reading the same as the health advisory?
No. The 3-hour PSI reflects recent conditions over a short period, while Singapore’s health advisory uses 24-hour PSI and PM2.5 information. NEA explains its air-quality reporting and advisory framework in its air pollution guidance. Since the readings cover different time periods, follow the current official health advisory instead of treating a short-term PSI value as interchangeable with it.
Conclusion
Haze in Singapore is shaped by fires beyond its borders, dry conditions, and winds that carry smoke toward the island. Its effects depend on pollution levels and how long people are exposed, so check NEA’s official health advice during haze episodes and adjust outdoor activity accordingly.
Because smoke crosses borders, lasting progress also depends on sustained regional fire prevention. Singapore can prepare for haze, but reducing fires where they start requires continued regional cooperation, as efforts such as regional cooperation to reduce cross-border haze illustrate.
