Will water temperature affect your triathlon race-day swim?

Arrive at any triathlon and the biggest talking point of the morning is only usually one thing – what’s the water temperature? Let’s face it, a chillier-than-expected swim will send a (literal) nervous shiver down the spines of most triathletes.

Conversely, a late-season triathlon with blistering hot weather and warm water may leave you wondering if you have to wear a wetsuit – or worried that you may not be allowed and lose all that extra buoyancy!

Handily though, there are rules governing water temperatures at many triathlons, which are published as part of the British Triathlon Federation (BTF) competition rules which you can read in full here (with 2023 amendments).

To save you trawling through them though, below is our simple guide to how it all works and how you can train smart to prepare for every eventuality!

It’s worth noting, though, that these guidelines apply only to events run under a Home Nation Association Event Permit, so check when you enter that your event falls under one of these.

We’re only going to cover the British Triathlon guidelines in this piece too, so if you’re racing overseas you may want to check out the World Triathlon regulations.

Some other events will have their own rules too – for example, Norseman is famed for often having a very chilly swim.

So do a little research on your chosen event first and the conditions you’ll be swimming in, if you’re not a fan of the cold!

Will I be able to wear my wetsuit?

This one is often the biggest concern for triathletes, especially if they don’t swim outdoors all year round to maintain their acclimatisation – or do not enjoy swimming outdoors without a wetsuit on.

Wetsuits add buoyancy which, combined with the hydrophobic coating on the neoprene, can make weaker swimmers feel more confident and swim faster.

The British Triathlon competition rules take into account the water temperature (taken one hour before the swim is due to start). This is measured at three points within the body of water (one in the middle and two in other areas) at a depth of 60cm.

If you think about it, this is around the depth your arms will reach as you swim, so takes into account the area of water you will be actually exposed to – and how much sun or rainfall may have warmed or cooled the top layers of water just before the race starts.

The first rule to be aware of is 4.2, which relates to wetsuit use and is shown here:

4.2 Wetsuit use:

International competitions (that is to say competitions run outside Great Britain) that are run under World Triathlon Competition Rules will adhere to those rules for wetsuit usage; competitors taking part in these should familiarise themselves with these differences.

a.) The use of wetsuits is forbidden or mandatory if the following combinations of distance and water temperature are attained:

b.) It is recommended that wetsuits are worn by all novices and Age-Groupers up to and including age 59 up to 22°C, and all novices and Age-Groupers age 60 and above up to 24.6°C

As well as showing us the mandatory and forbidden temperatures for wetsuit use, this table also shows that for distances up to 1,500m (so covering supersprint, sprint and Olympic-distance races) your wetsuit will be optional between water temperatures of 14℃ and 22℃ (24.6℃ for athletes over 60).

If you’re a strong swimmer and don’t need your wetsuit for speed or buoyancy, then you may wish to consider going wetsuit-free as you will save time in transition.

But just make sure you’re well-acclimatised to the temperatures likely on race day and can comfortably complete the distance without getting too chilly or risking your health. There’s still a good measure of personal responsibility within these guidelines!

What if I am worried about being too cold?

For swimmers worried about being cold at lower temperatures, try and make sure you’re swimming outdoors regularly in the lead-up to your event. You don’t need to swim the actual race distance at these sessions, but just get used to immersing yourself in the water and relaxing your body to avoid cold water shock.

Build up gradually over a few weeks, until you’re (hopefully) able to feel comfortable with the full distance by race day. You can still work on endurance in the pool.

Under the BTF guidelines on kit, your wetsuit can be up to 5mm thick, so if you feel the cold think about your wetsuit choice and makes sure it fits you correctly. A thicker suit will be warmer than a suit made from very thin neoprene (see our best thermal wetsuit reviews for more).

You’re also allowed to wear swim socks under British Triathlon guidelines (as long as they are tucked into your wetsuit legs) but gloves are classed as illegal equipment as they could give an advantage (by increasing the surface area of your hands) so by race day, ensure you are used to swimming without them!

A full list of permitted and illegal equipment for the swim leg can be found in section 4.12.

Some races do permit additional kit, though, such as some of the XTri series, where competitors can be swimming long distances in colder waters.

For example, Norseman allows use of neoprene accessories (but not gloves) and thicker neoprene – so check the rules for your individual race before you start worrying too much.

Provided you’ve done multiple swims before your race and acclimatised, there are still a few things left that you can do to help on race day.

As much as possible, try and stay warm before the swim start (if you’re cold before the swim you will be even colder once you get in!) so if it’s a chilly morning stay in shelter as long as you can.

Once on your way to race start, see if you’re able to pass your changing robe to someone just before you get in the water to keep it on for as long as possible and try and wear a pair of old flipflops to walk to the start (many race organisers will collect them and have them ready for you at the finish).

Some races will allow you to get in the water before to acclimatise and/or have an in-water start. If this is the case, use the time to calm your breathing and get used to the water.

Allow a little time to get into your wetsuit and once your breathing is settled, splash your face and then put your face in and blow some bubbles to avoid that breathless feeling once you get started.

You may find you have a few minutes in the water, so if this is the case, move around a little – do some sculling on your front, or a little aqua jogging to keep moving.

How will cold water affect an event’s swim distance?

The second main rule that could affect your swim is rule 4.4, which looks at how swim distances will be altered by water temperature on the day.

You will be pleased to read that certain modifications are made to British Triathlon guidelines based on unusually cold temperatures.

These state that: “At temperatures below 11°C open-water swimming in competition cannot take place. The above temperatures are based on water temperatures alone and assume that the wind chill factor is negligible. If wind chill is significant, swim distances may be reduced at higher temperatures.”

This will be down to the Chief Technical Official on race day to decide and announce, so listen carefully for any announcements on race day. The other guidelines are summed up in this table:

Again, the weather conditions on the day can affect the swim too:

“If other weather conditions dictate, i.e. high winds, heavy rain, changing temperature, current, etc. the Event Organiser in consultation with the Chief Technical Official may adapt limits of the swim length or adopt provisions about the use of wetsuits.”

Within the table above, though, you can see that most triathlons will not allow you to swim under 11°C and that between 11 and 13°C swim distances are limited.

It’s worth thinking about the race distance you’ve entered and seeing what distance you’ll be expected to swim at lower temperatures and making sure you’ve acclimatised and trained accordingly.

So, for example, if you’re racing an Olympic-distance with a 1,500m swim, at 12°C you’ll only swim 1,ooom, whereas at 13°C or over you’ll be expected to complete the full distance.

Rules also state that: “Where the average measured temperature is 27°C or below, the lowest measured temperature will be considered as the official water temperature.

“Where the average water temperature is above 27°C, the highest measured temperature will be considered the official water temperature.”

One good tip if you’re worried about water temperatures is to enter an event with similar water to that which you are training in.

For example, in mid-summer shallower lakes will heat up quickly and be warmer than deeper lakes or the sea. Early in the season, though, the sea may still be a little warmer than some cooler deep lakes or those further north.

What if wetsuits are forbidden in my race?

Once the water temperature reaches 22°C (or 24.6°C if you’re aged 60+ or are racing over 1,501m) wetsuits are forbidden under British Triathlon rules. Next to chillier conditions, this is the one scenario that can create a lot of panic amongst athletes!

Key here are two things: planning and preparation. Make sure you are prepared, but also try to think through why swimming without your wetsuit makes you nervous and try to address these nerves before race day.

Many UK lakes will reach their highest temperatures in August and temperatures of 22 or 24°C are not unheard of if we have a hot season.

With the average UK swimming pool heated to around 28°C you can see things will be a little cooler than the pool (and a breeze or rain will make a difference) but not dramatically so.

Getting used to swimming in open water without a wetsuit will be the most important thing you can do here – so if it looks possible your swim may be non-wetsuit, get used to taking your suit off at the end of each training swim and doing a short distance without it to see how it feels.

Gradually extend the distance you swim without it until you have more confidence in your body’s ability.

Beyond the temperatures, we can often perceive our suits a bit like a body of ‘armour’ against anything the water holds… Such as weeds, creatures and other kicking and splashing triathletes!

For these kind of worries, again try and approach them gradually with some exposure to the concerns during your more relaxed, training swims.

The more you acclimatise to swimming without your wetsuit, the more you’ll relax and feel more comfortable. Leaving it until race day and hoping for the best (unless your swim will definitely allow wetsuits) can be a recipe for disaster.

Joining a local tri club can help here, too, as you can join their open-water swim sessions and get used to swimming around other people. You’ll also learn some good tactics for race day!

If you’re a nervous open-water swimmer, maybe enter a race for your first one that either takes place in the venue where you normally swim, or somewhere similar, as familiarity can really help with race day nerves.

If that isn’t possible, arrive at our race location a day or so early so you can swim in the water and get used to it before the actual race.

Finally comes the issue of swim strength and ability. If you prefer wearing your wetsuit to compensate for poor technique – such as sinking legs, poor body rotation or poor body position – then getting a couple of sessions with a swim coach under your belt to address these before race day will be of huge help to you.

Many coaches are used to seeing these and with a few tweaks can often make a huge difference to your swimming and confidence!

For speedy swimmers looking for marginal gains on the other hand, losing your wetsuit may help you feel more ‘free’ when you swim but can make you a little slower if you’re benefitting from the suit’s technology.

In these instances, you may want to wear a swimskin – and these are permitted – but bear in mind that the British Triathlon rules stipulate:

“In standard distance and shorter events, swim skins must be worn for the whole event. For other distances, swimskins may only be removed if changing facilities are provided by the Event Organiser”.

Not only might racing your whole event in a swimskin be a little uncomfortable, but if you’re planning to wear one you will need to weigh up the time you need to spend wriggling out of it in transition versus the time you save by wearing it!

What should you do after a colder triathlon swim?

One final thing to mention here. Due to the afterdrop effect our core body temperature will continue to drop after we get out of cooler water so that, combined with wearing a damp tri-suit and the wind chill you get when cycling can lead to you feeling very shivery indeed – not ideal when operating a bike.

In these instances, make sure you have some extra kit to put on when you exit T1 such as a light bike jacket or gilet, arm warmers, a skull cap for under your helmet and gloves.

You may also want to add socks under your bike shoes – we’ve done races where our feet were still numb once we started the run, which was a weird (and not pleasant) experience!

If wearing an extra layer, just make sure your race number is on top with the number facing backwards – an elasticated race belt is the easiest way to achieve this.

Plus, be mindful that any kit you plan to remove will need to be stashed somewhere until you get back to transition, so if keeping warm is your top priority, take the hit on weight and add some storage to your bike (such as a top tube bag or saddle bag) – or find a tri-suit with large rear pocket you can stuff things into!

Top image credit: Castle Triathlon Series