Llyn Cau Water Temperature Today
Llyn Cau, a flooded quarry swim site in Wales, United Kingdom. The water runs cold all year, so most swimmers wear a wetsuit, and is near-freezing in midwinter.
In August Llyn Cau averages about 15°C, peaking near 15°C in July, August, September and dropping to roughly 3°C at its coldest.
River and swimming-hole temperatures are modelled from long-term monthly averages and refined with live air temperature, wind and UV. Moving water reacts faster to the weather than a lake or the sea.
Llyn Cau water temperature by month
| Month | Average water temperature | Swimming |
|---|---|---|
| January | 3.8°C | cold |
| February | 3.0°C | cold |
| March | 3.8°C | cold |
| April | 6.0°C | cold |
| May | 9.0°C | cold |
| June | 12.0°C | cool |
| July | 14.2°C | cool |
| August | 15.0°C | mild |
| September | 14.2°C | cool |
| October | 12.0°C | cool |
| November | 9.0°C | cold |
| December | 6.0°C | cold |
Llyn Cau swim conditions FAQ
What is the water temperature in Llyn Cau right now?
In August the water in Llyn Cau averages about 15°C. We refine that long-term average with today's air temperature, because this flooded quarry responds quickly to the weather.
When is the best time to swim in Llyn Cau?
Water here stays below 18°C all year, peaking near 15°C in July, August, September. Most swimmers use a wetsuit and keep swims short.
Can you swim in Llyn Cau in winter?
Yes, but winter temperatures drop to roughly 3°C. Below 12°C, cold-water shock is the main risk: enter slowly, never swim alone, and limit time in the water.
Is Llyn Cau safe for swimming?
Moving and inland water carries different risks from the sea: check flow after rain, avoid weirs and undercut banks, look for submerged rocks before jumping, and respect local access rules and water-quality notices.
Water safety tips
- Check the flow rate after heavy rain — inland water can rise and speed up within hours.
- Never jump before checking depth and submerged rocks; levels change through the season.
- Enter slowly to control cold-water shock, and get out before you start shivering.
- Swim with someone else and agree an exit point downstream before you start.
- Flooded quarries are deep and steeply shelved, with sharp thermoclines a metre or two down.
- Winter water here can be near freezing; treat it as a cold-water swim.
Swim season here: cold-water swimming all year.
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