Haze, heat, and climate preparedness

Short answer: Use haze.gov.sg or myENV rather than a random AQI widget. The 1-hour PM2.5 reading tells you what to do now; the 24-hour PSI is what you plan tomorrow around, and it's what MOH's advisory bands key off. N95s are for people stuck outdoors for hours in bad haze, not for the commute or the living room, and a HEPA purifier sized for the bedroom does more for a sensitive household than a drawer full of masks. And treat heat as the year-round risk: NEA's heat stress level on myENV tells you when to move the run or the CCA.

Transboundary haze is intermittent but memorable, which is why it dominates the conversation about weather here. Heat stress is annual, and nobody posts about it. Flash floods are the third climate surprise renters tend not to check for (flood and rental site checks), thunderstorms and high-floor lightning anxiety are the fourth (lightning and thunderstorm living), and dengue-cluster weeks are the fifth (cluster and fogging ops).

New arrivals routinely confuse third-party AQI apps with Singapore's official PSI and 1-hour PM2.5 readings. NEA is blunt about it: indices on other websites are computed differently, aren't comparable with the 24-hour PSI, and may run on low-cost sensors. So you end up either cancelling a fine morning or going for a run on a genuinely bad one.

When haze arrives

Haze here is smoke from forest and peat fires in the region, made worse by dry weather, low rainfall and a change in wind direction. NEA says it reaches Singapore particularly during the Southwest Monsoon, which runs from June to September, and the Meteorological Service notes that slight to moderate haze is also common in light winds during the inter-monsoon months, which include October and November.

It isn't every year. In 2026 the 24-hour PSI went into the Unhealthy range on 4 September, the first time since 8 October 2023. When haze sets in, NEA issues a daily haze advisory with a forecast range for the 24-hour PSI over the next 24 hours, on haze.gov.sg, nea.gov.sg and the myENV app. Buy masks and sort out a purifier in May, not on the first smoky morning.

Two numbers, two jobs

The reason for the split is that the scientific health evidence is largely built on 24-hour exposure. That is why MOH advisories key off PSI bands even while you're watching the hourly PM2.5 chart twitch.

For the hourly number, there's a personal guide, drawn up by MOH and the environment ministry, that covers the next hour only:

"Vulnerable" here means the elderly, pregnant women, children, and anyone with chronic lung or heart disease. Readings are reported for five regions (North, South, East, West, Central), so use the one you're actually in, or the nearest.

Don't judge by the sky. NEA points out that poor visibility doesn't by itself mean dirtier air, because humidity and rain cut visibility too, and the burning smell usually, but not always, lines up with a rise in the readings.

What to do when PSI rises

This is MOH's advisory, by 24-hour PSI:

MOH's definitions are precise. Prolonged means continuous exposure for several hours, strenuous means a lot of energy or effort, reduce means do less, minimise means do as little as possible, and avoid means don't.

For healthy people, a few days of haze generally means irritated eyes, nose and throat and not much more, and MOH says outdoor activity is still safe in most cases. Drink plenty of water. If anyone in the house has a heart or lung condition, read the section on that below.

Masks: when an N95 helps

MOH's line is clearer than most people expect. N95 masks aren't needed for short exposure like commuting from home to school or work, and they aren't needed indoors. A healthy adult who has to be outdoors for several hours when the PSI is Hazardous (above 300) may reduce exposure with a well-fitted N95.

The bar is lower for vulnerable people. The elderly, pregnant women and anyone with chronic heart or lung disease should avoid or minimise outdoor activity once the PSI is above 200, and if they must be out for several hours, an N95 may cut their exposure. N95s make breathing harder work, though, so the elderly, pregnant women and people with severe heart or lung problems who struggle to breathe at rest or on exertion should ask their doctor before using one. MOH also says women in the second and third trimesters should stop wearing one if it's uncomfortable.

What actually filters haze:

• N95 or FFP2. A NIOSH-approved N95 has "NIOSH" and "N95" printed on its packaging. The European FFP2 (EN 149) is the closest equivalent, according to NEA.
• Not surgical masks. They don't filter fine particles. They can ease the discomfort by blocking larger irritant particles, and that's all.
• Fit over brand. Air that leaks round the edges skips the filter, so check the mask is the right size and covers nose and mouth without leaking. MOH notes that an imperfect fit still filters some of the haze, so don't give up on it.
• Reuse is fine. Change an N95 when it's soiled or out of shape, and don't share them.

Children and masks

N95 certification was developed for adults at work, and NEA says there's no international certification standard for children's masks. So the protection for kids is the MOH table, not a mask: minimise prolonged or strenuous outdoor activity once the forecast is Unhealthy, minimise all outdoor activity at Very unhealthy, and keep them indoors when it's Hazardous. If a child really has to be outside, NEA says a mask that's been tested on children can be used where necessary, as long as it keeps a good seal, and it comes off if the child finds breathing uncomfortable. Children with asthma or a heart condition can react differently to a mask, so ask their doctor first.

Masks are sold at major pharmacies and supermarkets, and the government may release its national N95 stockpile to them if more are needed. Buy sizes that fit each adult before the season, while you can try them on at leisure.

Purifiers and keeping haze out of the flat

PM2.5 gets into buildings through gaps and fresh-air intakes, and indoor levels can build up, so the home set-up matters more than any mask. NEA's household tips:

• Close doors and windows when the outdoor air is getting worse, and reopen them when it improves.
• Mop or wipe instead of dry dusting or vacuuming, which stirs settled dust back up.
• Cut indoor sources like cigarettes and candles.
• Fans and aircon are fine. If a unit draws in unfiltered outside air, as window units do, close its outdoor air intake.
• Run a portable air purifier to bring indoor particle levels down further.

Choosing the purifier:

• Filter. NEA prefers HEPA (High Efficiency Particulate Air) filters for fine particles.
• Size it with the smoke CADR. Clean Air Delivery Rate labels carry three numbers (smoke, dust, pollen), and smoke is the one for haze. NEA's rule is a smoke CADR, in cubic feet per minute (cfm), of at least three times the room's volume in cubic metres. If the box gives it in cubic metres per hour, you need at least five times the volume. A 4 m by 3.5 m bedroom with a 2.6 m ceiling is about 36 cubic metres, so look for a smoke CADR of about 110 cfm, or about 180 cubic metres per hour.
• Close the room. NEA warns that purifiers may not reach their rated performance with doors and windows open. Don't wedge it into a corner where the airflow is blocked.
• Buy for the filter, not the ioniser. NEA's technical advisory on air-cleaning technologies, written during COVID-19, says electronic air cleaners such as ionisers may give off ozone and other by-products that could irritate the airways or skin, and recommends sizing a unit on the smoke CADR of its filters alone.
• No CADR label? NEA says many effective purifiers don't have one. Ask the manufacturer for evidence of how well it removes fine particles. NEA also keeps a reference list of portable air cleaners on haze.gov.sg, based on suppliers' data.

Check the filter before June and buy a spare. NEA's advice is to replace filters on the manufacturer's schedule. If the PSI crosses 200 and home isn't coping, the government's 2026 haze plan put air-conditioned rooms at every Community Centre or Club on standby for anyone who needs respite.

Asthma, heart and lung conditions

MOH's instruction for people with chronic heart or lung conditions is to keep medication on hand and readily available. A few more things are worth knowing:

• Symptoms can lag. NEA says there can be up to one to three days between exposure and health effects, so a wheezy child on Tuesday may be reacting to the weekend's haze.
• Don't wait it out. NEA advises seeing a doctor if you develop breathing difficulties. Vulnerable people who feel unwell or develop symptoms should get medical attention promptly, even when the PSI is only Good or Moderate.
• Severe breathlessness is a 995 call. Breathlessness, loss of consciousness and seizures are all on SCDF's list of emergency examples.
• Inhalers go to school. MOE asks parents to make sure children carry medication such as asthma inhalers, or to keep them at home.

If you haven't got a GP yet, sort that out before the season, along with a paediatrician if you have kids. Healthcare GPs and hospitals explains how the system fits together.

Schools and preschools

MOE schools follow a set plan keyed to the 24-hour PSI forecast, and they also adjust through the day using the 1-hour PM2.5 readings. Every classroom has an air purifier.

MOE considers closing schools when the next day's forecast is Hazardous, announces it around the same time as the health advisory, and warns that notice can be short. If you can't arrange care, you can still send your child in and teachers will supervise. School-based student care keeps running for existing students. More on the system in local schools for expat children.

For preschools, ECDA tells centres to minimise prolonged outdoor activities and strenuous indoor physical activities once the air is Unhealthy, and children with chronic heart or lung conditions are exempted from outdoor activities and exercise. All preschools have air purifiers, with at least one enclosed room kept ready for children who feel unwell. See preschool and childcare for how centres work.

MOE's plan is written for its own schools. If your child is at an international school, ask before the season which reading it goes by, when outdoor PE, CCAs and fixtures stop, and how it tells parents about a closure.

Work, and a helper at home

Your own job

Under the Workplace Safety and Health Act, the duty to assess the haze risk and act on it sits with your employer. For office staff, the parts that matter are these. Employers are strongly encouraged to allow flexible work arrangements such as working from home and staggered hours, especially for older, pregnant and chronically ill staff. They're also asked to be flexible about leave if you're unwell or looking after a family member. If an employer suspends operations because of haze, MOM says it should bear the cost and not deduct wages or leave. MOM's general line for haze concerns is 6438 5122.

If you employ a domestic helper

MOM's haze guidelines are written for employers whose staff work outdoors, which MOM defines as work done outside buildings regularly or most of the time. Its haze pages have no separate section on domestic helpers. So apply MOH's table to her exactly as you would to anyone else in the household, and plan her outdoor chores around the readings:

• Dog walks and walking school runs. Keep them short. A commute-length trip is the kind of exposure MOH says doesn't need an N95. Drop the long walk when the PSI is Unhealthy or worse.
• Heavy or long outdoor jobs. Car washing, scrubbing a patio or a big outdoor clean-up can wait for clear air.
• Hours outside at Hazardous. If it really can't wait, give her a well-fitted N95, as MOH suggests for anyone outdoors for several hours at that level.
• Her own health. If she's pregnant, older, or has asthma or a heart condition, the doctor question applies to her too. Make sure she knows to tell you if she feels unwell.

MOM explains why outdoor workers are given masks at a lower PSI than the public: their jobs can mean prolonged or strenuous outdoor work on a regular basis. Most of a helper's outdoor time is short, so the public advice usually fits. If she's actually doing hours of outdoor work, the worker logic applies. For the wider employer side, see hiring a domestic helper.

Heat, the year-round risk

Heat is what gets newcomers, because it's there every week and there's no smoke to warn you. NEA's Heat Stress Advisory runs on the Wet Bulb Globe Temperature (WBGT), which combines air temperature, humidity, wind and sun into one number. The Meteorological Service reports it as a 15-minute average, updated every 15 minutes, on myENV and weather.gov.sg.

The advisory is for prolonged outdoor activity like a run, a hike or a match, not the short walk between the MRT and the office. Moderate and High usually show up in the late morning and afternoon, and High is more common in the hotter months of April and May. Nights aren't automatically safe either. The Meteorological Service notes that humidity above 85% at night slows the evaporation of sweat, so go easy on hard evening sessions too.

NEA's list of people who should take extra care includes the elderly, children and infants, pregnant women, people who are ill, recently recovered or living with a chronic condition, and people who've recently travelled from a cooler climate. That last one is you. The WSH Council tells workers not to over-exert themselves in their first two weeks, especially if they've just arrived from a cooler country, and to build up heat exposure gradually over at least seven days. The same logic applies to your runs. Sports and fitness in Singapore covers timing your training, and what to wear covers the clothing side.

Children follow their school's guidance rather than the public advisory. In a heatwave, MOE says schools watch the region-specific heat stress level and may cut the intensity of activities, move them to cooler times, add rest and water breaks, or suspend outdoor physical activities. Outdoor workers follow MOM's heat guidelines, and athletes follow Sport Singapore's.

Heat exhaustion or heat stroke

Early heat illness shows up as weakness, dizziness, vision problems, intense thirst, nausea, headache, vomiting, muscle cramps, breathlessness or palpitations. Resting somewhere cool with a cool drink (water, clear juice or a sports drink) usually sorts it. Ignored, it can progress to heat stroke.

Heat stroke is the dangerous one: disorientation, partial or complete loss of consciousness, seizures, and a core temperature often above 40°C. It isn't only a risk for the frail. Exertional heat stroke hits relatively fit people doing prolonged, strenuous exercise, which is exactly the new arrival who runs at noon.

Call 995 for any of those signs. Loss of consciousness and seizures are both on SCDF's list of emergency examples. While you wait, the WSH Council's first aid is to move the person somewhere shady or cooler, loosen or remove their clothing, apply cool water and fan them, and put ice packs under the armpits and in the groin.

Household kit

• N95 or FFP2 masks that fit each adult, bought before June
• A HEPA purifier with enough smoke CADR for each bedroom you'll close up, plus a spare filter
• Inhalers and regular medication topped up for anyone with asthma or a heart or lung condition
• Water bottles for kids' outdoor CCAs in the heat, haze or no haze
• myENV installed and haze.gov.sg bookmarked, so you're never relying on a foreign AQI widget alone
• A backup care plan for a short-notice school closure

When PSI spikes, reschedule the outdoor sport and don't make a production of it. This is ordinary regional weather politics meeting biology, not a personal failure of tropical toughness.

Next up: emergencies for 995 and 999 literacy, and finding a paediatrician if there are kids in the household.