Is It Safe to Swim During Haze Season in Singapore?

By Coach Tan Meng Chew (MC), Founder and Head Coach, SG Sink or Swim

Every year, usually somewhere between July and October, a familiar haze descends over Singapore, drifting in from land and forest fires in parts of Sumatra and Kalimantan. The skyline turns a hazy grey-yellow, the smell of smoke becomes noticeable even indoors, and parents across the island start asking the same practical question: is it actually safe to keep swim lessons going, or should we be pausing pool time until the air clears?

I run SG Sink or Swim, a Singapore-based swim coaching brand, and haze season is genuinely one of the more operationally complicated stretches of the year for anyone running outdoor swim programmes here. It's also a period where I see a lot of understandable confusion among parents — some pausing all outdoor activity the moment the sky looks slightly grey, others continuing lessons as normal without checking anything at all, and very few actually consulting the specific, practical guidance that Singapore's National Environment Agency (NEA) provides for exactly this situation.

This article is meant to walk you through, in real detail, how to think about swimming — and outdoor activity generally — during haze season: how Singapore's air quality monitoring system actually works, what the different readings mean in practical terms, how to interpret them specifically for swimming and pool activity, and what a genuinely sensible, safety-conscious approach looks like for your family or for a swim programme you're enrolled in.

Understanding How Singapore Actually Measures Haze

Before getting into swimming-specific guidance, it helps to understand the two main measurements NEA uses, because a lot of parental confusion comes from not knowing which number to look at for which purpose.

The 24-hour PSI (Pollutant Standards Index). This is a rolling average of air pollutant concentrations over the preceding 24 hours, giving a broader picture of prevailing air quality conditions rather than a single instantaneous reading. NEA publishes bands for this index — broadly, a reading up to 50 is considered Good, 51 to 100 is Moderate, 101 to 200 is Unhealthy, 201 to 300 is Very Unhealthy, and above 300 is Hazardous. This 24-hour figure is the number NEA recommends using specifically for planning ahead — deciding, for instance, whether tomorrow's outdoor swim lesson should proceed as normal, be modified, or be postponed.

The 1-hour PM2.5 concentration reading. PM2.5 refers to fine particulate matter small enough to be inhaled deep into the lungs, and it's the pollutant most directly responsible for the health effects associated with haze. Unlike the 24-hour PSI, this reading is designed to reflect real-time, immediate conditions, since haze intensity can shift meaningfully within a single day depending on wind direction and the scale of fires in the region. NEA publishes this reading in bands as well, and it's specifically the number recommended for a same-day, immediate decision — checking right before you're about to head to the pool, rather than planning a day ahead.

The practical takeaway from this distinction: if you're planning tomorrow's swim lesson or a weekend pool outing in advance, check the 24-hour PSI forecast. If you're already dressed and about to walk out the door for a lesson happening in the next hour or two, check the current 1-hour PM2.5 reading instead, since conditions may have shifted since the previous day's forecast was issued.

Both figures, along with official health advisories, are published on NEA's haze microsite and the myENV mobile app, and I'd genuinely encourage every parent in Singapore to have at least one of these bookmarked or installed during haze season, rather than relying on how hazy the sky looks by eye, which is a genuinely unreliable proxy for actual particulate concentration.

Why Visual Haze Isn't a Reliable Guide on Its Own

This is worth stating plainly because it surprises a lot of parents: how hazy the air looks isn't a dependable indicator of how unhealthy it actually is. Haze intensity as perceived visually depends on factors like humidity, time of day, and lighting conditions, which don't map cleanly onto actual particulate concentration. I've seen days where the sky looked only mildly hazy but PM2.5 readings were meaningfully elevated, and other days with a more visibly thick, yellow-tinged sky where readings were closer to moderate. Relying on what you can see out the window, rather than checking the actual published readings, is one of the more common mistakes I see families make during haze season, in both directions — sometimes cancelling activity unnecessarily on a day that's actually fine, and sometimes continuing outdoor swim time on a day where the numbers would have suggested more caution.

What the Different Bands Actually Mean for Outdoor Swimming

NEA's official activity guidelines, developed specifically to help the public and organisations like schools and sports facilities make sensible decisions during haze, generally scale advice according to severity, moving from normal activity, through reducing prolonged or strenuous outdoor activity, to minimising outdoor activity altogether, and finally to avoiding outdoor activity entirely at the most severe levels. Government agencies, including Sport Singapore, maintain haze management plans that translate these bands into specific operational guidance for sports and swim facilities — covering things like when strenuous outdoor training should be reduced, when outdoor activity should be minimised or avoided altogether, and additional precautions like ensuring adequate ventilation and making N95 masks available to staff at higher severity levels.

Swimming sits in a slightly particular category worth understanding specifically. On one hand, outdoor pool swimming is generally a lower-intensity activity for most recreational lessons compared to something like an outdoor running programme or football training, which somewhat reduces the volume of air a child or adult is drawing in during a session. On the other hand, breathing patterns during swimming — including the deep, sometimes rapid breaths taken between strokes, particularly during more vigorous stroke practice or breath-control drills — can involve meaningfully increased inhalation compared to standing still, and swim sessions often run for a sustained period, which matters because prolonged exposure, even at moderate pollution levels, carries more cumulative health impact than a brief exposure at the same level.

This is precisely why official guidance emphasises reducing prolonged or strenuous outdoor activity specifically at moderately elevated levels, before moving to a full recommendation to minimise or avoid outdoor activity altogether at more severe levels — the duration and intensity of the activity genuinely matters, not just whether it's happening outdoors at all.

Who Should Be Most Cautious

Health guidance around haze consistently emphasises that individual health status meaningfully affects how a given air quality level should be interpreted, and this matters directly for swim lesson decisions.

Children generally warrant extra caution compared to healthy adults, because children breathe at a faster rate relative to their body size and their respiratory systems are still developing, making them somewhat more sensitive to airborne particulate matter at a given concentration than a healthy adult would be at the same level.

Anyone with pre-existing respiratory conditions — asthma, chronic bronchitis, or other lung conditions — needs to be more cautious at lower pollution thresholds than the general population, and should generally follow more conservative guidance during haze periods, potentially avoiding outdoor swim activity at levels that might be considered acceptable for an otherwise healthy person.

Those with cardiovascular conditions are also generally advised to exercise more caution during elevated haze periods, since particulate exposure has documented effects on cardiovascular health, particularly during sustained physical exertion.

Pregnant individuals and elderly adults are typically included in the more cautious guidance categories as well, reflecting generally increased sensitivity to air quality effects.

If your child or family falls into any of these categories, I'd encourage a more conservative approach than the general population guidance suggests — checking readings more frequently, opting for indoor swim alternatives where available at lower haze thresholds than might apply to a generally healthy child, and consulting your paediatrician or physician directly if you're uncertain how a specific health condition should factor into haze-season activity decisions specifically.

Practical Guidance for Parents During Haze Season

Bringing this together into something genuinely actionable, here's how I'd encourage any parent to approach swim lesson decisions during a haze episode.

Check the 24-hour PSI forecast the evening or morning before a scheduled lesson, to get a general sense of whether the coming day's conditions are likely to be in a range where normal outdoor activity is reasonable, where more caution is warranted, or where postponing entirely is the sensible choice.

Check the current 1-hour PM2.5 reading close to the actual lesson time, since same-day conditions can shift meaningfully from an earlier forecast, particularly if wind direction changes over the course of a day.

Favour indoor pool facilities during moderate haze conditions where available, since indoor pools, particularly those in air-conditioned or filtered environments, generally offer meaningfully better air quality than being directly outdoors during a haze episode, even though the pool water itself is unaffected by haze either way.

Consider reducing lesson intensity rather than cancelling outright at moderately elevated levels, particularly for a lesson that would otherwise involve extended breath-control drills or vigorous stroke practice. A gentler session, or one that limits high-exertion segments, can be a reasonable middle ground rather than an all-or-nothing choice between full normal activity and complete cancellation.

Don't hesitate to postpone or reschedule during genuinely unhealthy conditions, even if it means disrupting a lesson schedule. A missed or rescheduled swim lesson has essentially no lasting impact on a child's overall progress; genuine, sustained exposure to unhealthy air quality carries real, if generally modest for a single episode, health risk that simply isn't worth trading for lesson consistency.

Keep an eye on your child's own symptoms during and after outdoor activity in hazy conditions — coughing, unusual fatigue, eye irritation, or breathing difficulty are signals to stop the activity and move indoors regardless of what the official readings say at that moment, since individual response can vary from the general guidance.

What a Responsible Swim Programme Should Be Doing During Haze Season

If you're enrolled in swim lessons with any provider in Singapore, it's worth knowing what a genuinely responsible approach to haze season looks like on the programme side, so you can evaluate whether your own child's provider is handling it appropriately.

A responsible programme should be actively monitoring NEA's published readings, not just responding after visible haze becomes obvious to the naked eye, and should have a clear, communicated policy for when outdoor sessions get modified, moved indoors where possible, or postponed, rather than leaving that judgment call informally to whichever coach happens to be on deck that day. It should communicate proactively with families when haze conditions are likely to affect a scheduled outdoor session, rather than waiting for a parent to ask. And it should be willing to genuinely adjust or reschedule sessions during unhealthy conditions, even at some inconvenience to the programme's own scheduling, rather than prioritising lesson-count consistency over the health guidance appropriate to the day's actual conditions.

At SG Sink or Swim, this is exactly the kind of judgment I apply across our own outdoor lesson scheduling during haze season — treating NEA's published readings, not visual impression or scheduling convenience, as the actual basis for whether a given outdoor session should proceed as planned, be adjusted, or be postponed, and staying in direct communication with families whenever haze conditions are likely to affect a scheduled lesson.

Preparing for Haze Season in Advance

A few practical steps worth taking before haze season typically arrives each year, roughly from mid-year through the last quarter, based on the pattern of regional dry-season land and forest fires that typically drive it.

Bookmark NEA's haze microsite or install the myENV app ahead of time, so checking current readings becomes a quick habit rather than something you're scrambling to find during an actual haze episode.

Identify indoor pool alternatives near you in advance, so you have a ready backup option rather than needing to research this for the first time in the middle of a haze episode when you'd rather just make a quick decision.

Have a conversation with your child's swim coach or programme ahead of haze season about their specific policy for haze-affected outdoor sessions, including how make-up lessons are handled if a session needs to be postponed, so there's no ambiguity or awkwardness when the situation actually arises.

If your child or family has any relevant respiratory or cardiovascular health considerations, it's worth having a brief conversation with your physician ahead of haze season specifically about what activity thresholds are appropriate for your particular situation, rather than working this out reactively once conditions have already become poor.

A Word on Not Overreacting

While I've spent most of this article emphasising genuine caution, it's worth balancing that with a note against overreaction, because I do see some families swing too far in the opposite direction — cancelling all outdoor activity at the very first hint of haze in the air, even when actual readings remain in the Good or Moderate range where normal activity is genuinely fine for most healthy individuals, including children.

Singapore's haze episodes vary considerably in severity from year to year and even day to day within a single episode, and treating every hazy-looking day as automatically dangerous, without actually checking the published readings, leads to unnecessary disruption to swim progress and general outdoor activity that isn't actually warranted by the real conditions. The entire point of checking the specific PSI and PM2.5 readings, rather than going by visual impression or general anxiety, is to make decisions that are genuinely proportionate to actual risk — neither ignoring real unhealthy conditions nor needlessly restricting perfectly safe activity based on how ominous the sky happens to look on a given afternoon.

Final Thoughts From Coach MC

Haze season is simply part of life in Singapore, recurring most years with varying intensity, and the sensible approach isn't to treat it as either a non-issue to be ignored or a reason to pause all outdoor swimming activity for weeks at a time. It's to build the habit of actually checking NEA's published 24-hour PSI and 1-hour PM2.5 readings before planning and before heading to an outdoor pool session, understanding what the different bands mean for outdoor activity generally and swimming specifically, paying extra attention if your child or family falls into a more sensitive health category, and being willing to adjust, move indoors, or postpone a session when the actual numbers genuinely call for it, rather than either ignoring the guidance or overreacting to visual haze alone.

Whatever swim programme your family is part of, I'd encourage you to ask directly how they approach haze-season decision-making, and to build your own habit of checking the official readings rather than relying on the sky's appearance. Get that habit in place, and haze season becomes a manageable, well-informed part of your family's swim routine, rather than a source of constant uncertainty every time the air looks a little grey.

Stay safe, breathe easy, and see you at the pool.

— Coach Tan Meng Chew (MC), SG Sink or Swim