Optimal_T

 

I was asked about the best conditions for learning to swim...

Copilot:

What is the temperature of the Richelieu River late June?

The best grounded estimate for late June water temperature in the Richelieu River (downtown Saint‑Jean‑sur‑Richelieu) is around 20–22 °C, based on the available regional data and how the river behaves thermally.

Here’s how we know this:

⭐ 1. Direct regional measurement near the Richelieu (June 28, 2026): ~21 °C

Environment Canada’s marine/river summary for the Richelieu–Lake Champlain system shows a water temperature of 21 °C on 28 June 2026 at a nearby monitoring point. 

This is the strongest late‑June datapoint available.

⭐ 2. Downtown Saint‑Jean gauge (À St‑Jean)

The RiverApp listing confirms that the À St‑Jean gauge does provide water temperature, but the snippet does not show the actual value.   

Given the river’s thermal behavior and the regional measurement above, downtown Saint‑Jean is almost always within ±1 °C of the regional Richelieu reading.

⭐ 3. How the Richelieu behaves in late June

The Richelieu is:

shallow

slow‑moving

directly fed by Lake Champlain

Lake Champlain typically reaches 19–22 °C in late June, and the Richelieu tracks it closely.

This matches the 21 °C Environment Canada reading.

🎯 Best estimate for downtown Saint‑Jean in late June

≈ 20–22 °C

This is consistent with:

the Environment Canada June 28 measurement (21 °C)

typical Lake Champlain late‑June temperatures

the river’s shallow, warm characteristics

If you want, I can pull live temperature from the downtown gauge (À St‑Jean) if you give me the exact RiverApp or Québec Sécurité Publique link you use.

Is this too cold to swim in?

Short answer, Louise: No — 20–22 °C is not too cold to swim in.  

But it is noticeably cool, and how it feels depends on what you’re doing and how long you stay in.

Here’s the clear breakdown so you can judge it for yourself.

🌡️ How 20–22 °C water actually feels

This temperature range is:

Refreshing

Cool at first

Comfortable once you’re moving

Too chilly for long, still floating sessions

Most people can swim comfortably for 20–40 minutes at 21 °C without feeling cold stress, especially if the air is warm.

It’s very similar to:

Lake Champlain in early July

Most Quebec rivers in summer

Open‑water triathlon temperatures (they often race at 20–22 °C)

So it’s absolutely swimmable.

🏊 Comparison to known standards

Competitive swimming pools:

26–28 °C → feels warm

Recreational pools:

28–30 °C → feels very warm

Open‑water races:

20–22 °C → normal

18–20 °C → cool

16–18 °C → wetsuit recommended

<16 °C → cold

So the Richelieu in late June is in the normal open‑water swimming zone.

🧠 Why it feels cooler than the number suggests

Water conducts heat 25× faster than air.

So 21 °C water feels like standing outside on a 10–12 °C day.

That’s why:

You feel a chill when you first enter

You warm up once you start swimming

You cool down quickly if you stop moving

🎯 Bottom line

20–22 °C is perfectly fine for swimming, especially if:

the air is warm

you’re actively swimming, not just floating

you don’t stay in for an hour

If you tell me what kind of swimming you’re thinking about — relaxing, exercise, wading, long swims — I can give you a more tailored comfort range.

But it is not optimal for learning to swim!!

You’re absolutely right, Louise — 20–22 °C is not optimal for learning to swim, even though it’s safe and swimmable.

And your instinct here is spot‑on: learning to swim is a very different experience from already knowing how to swim.

Let me break it down clearly and practically.

⭐ Why 20–22 °C is not ideal for learning

When someone is learning to swim, the biggest challenges are:

relaxing

controlling breathing

staying calm

focusing on technique

building confidence

Cool water works against all of these.

Here’s what happens in 20–22 °C water:

The body gets a cold shock on entry

Breathing becomes shallow and faster

Muscles tense up

Fine motor control drops

The learner feels rushed or uncomfortable

They tire more quickly

They want to get out sooner

All of this makes learning harder.

⭐ Optimal water temperature for learning to swim

For beginners, the ideal range is:

28–30 °C (82–86 °F)

This is the temperature used in:

swim lessons

physiotherapy pools

beginner classes

baby/toddler swim programs

senior swim programs

Warm water helps learners:

relax

float more easily

breathe calmly

stay in longer

focus on technique instead of discomfort

It’s a huge difference.

⭐ Why rivers and lakes feel harder for beginners

Natural water is almost always cooler:

Richelieu River late June: 20–22 °C

Richelieu mid‑August: 21–24 °C

Lake Champlain early summer: 19–22 °C

This is fine for confident swimmers, but beginners often:

tense up

lose buoyancy

struggle with breath control

feel unsafe

get tired quickly

So yes — it’s not optimal for learning.

⭐ A practical rule of thumb

If someone is learning to swim:

Warm pool = ideal

Warm lake = acceptable

Cool river = not recommended

The Richelieu is wonderful for confident swimmers, but not the best classroom.

⭐ If you want, I can help you with:

How to safely practice in cooler water

How long someone can stay in 20–22 °C without getting chilled

Techniques to stay relaxed in cooler natural water

How to judge water temperature by feel

Just tell me what direction you want to go.