Lake Llyn Trawsfynydd — Current Water Temperature, Annual Trends and Forecast
This page provides information on the current water temperature in Lake Llyn Trawsfynydd, trends, monthly ranges and the forecast for the coming days.
Current Water Temperature
Water Temperature in Lake Llyn Trawsfynydd today is 18.7°C.
Water Temperature: Daily Trends, Historical Records, and Forecast
⚠️ As of today, the minimum water temperature ranges from 65°F (18°C) to 68°F (20°C). This is already quite warm water, which is ideal for most people. Swimming becomes comfortable, and prolonged stays in the water do not cause discomfort. This temperature is perfect for family trips and for those who prefer warmer water. It is also comfortable for water sports such as surfing or swimming. It is important to note that these swimming tips and recommendations apply only in good weather. When the air temperature is below 68°F (20°C), and sometimes even below 77°F (25°C), swimming can be unpleasant even with relatively high water temperatures.
Water Temperature Chart Over the Last 30 Days
Table of Daily Sea Temperature Data
| Date | Current | Average | Forecast |
|---|---|---|---|
| AUG 6 | 19.0°C | 22.0°C | |
| AUG 7 | 19.0°C | 22.0°C | |
| AUG 8 | 19.0°C | 22.0°C | |
| AUG 9 | 19.0°C | 22.0°C | |
| AUG 10 | 18.7°C | 22.0°C | |
| AUG 11 | 18.7°C | 22.0°C | |
| AUG 12 | 18.7°C | 22.0°C | |
| AUG 13 | 18.7°C | 22.0°C | |
| AUG 14 | 22.0°C | 18.9°C | |
| AUG 15 | 22.0°C | 19.0°C | |
| AUG 16 | 22.0°C | 19.2°C | |
| AUG 17 | 22.0°C | 19.4°C | |
| AUG 18 | 22.0°C | 19.5°C | |
| AUG 19 | 22.0°C | 19.7°C | |
| AUG 20 | 22.0°C | 19.9°C |
* Current - Actual water temperature value
** Average - Average water temperature on this day in recent years
*** Forecast - Our water temperature forecast
Actual nearshore water temperatures may fluctuate by several degrees from the reported values, especially following heavy rainfall or extended periods of strong winds. Certain wind patterns can cause colder, deeper waters to rise and replace the sun-warmed surface water, leading to noticeable variations.
Our forecast is based on a proprietary mathematical model that considers real-time water temperature changes, historical trends, key weather patterns, wind strength and direction, and air temperature specific to each region. Additionally, we incorporate data from other resorts to enhance accuracy.
Monthly Water Temperature Range (Min, Max & Average)
| Month | Min | Avg | Max |
|---|---|---|---|
| January | 0°C | 4°C | 7°C |
| February | 1°C | 5°C | 8°C |
| March | 3°C | 7°C | 10°C |
| April | 7°C | 11°C | 14°C |
| May | 10°C | 17°C | 23°C |
| June | 13°C | 20°C | 26°C |
| July | 17°C | 22°C | 27°C |
| August | 17°C | 22°C | 27°C |
| September | 12°C | 18°C | 23°C |
| October | 9°C | 13°C | 17°C |
| November | 4°C | 8°C | 11°C |
| December | 1°C | 5°C | 8°C |
Lake Llyn Trawsfynydd: Water Temperature by Location
Lake Llyn Trawsfynydd: Weather Forecast
August 14
August 15
August 16
Location & Local Information
Llyn Trawsfynydd is a large artificial lake in Snowdonia National Park, created in the 1920s to supply water for a nearby hydroelectric station. Surrounded by rugged hills and open moorland, it lies at a relatively high altitude, which keeps the water cool throughout the year. In winter, the surface temperature often falls to around 3–5 °C (37–41 °F), while in spring it gradually rises to about 8–10 °C (46–50 °F). During the summer months, the lake can reach 14–16 °C (57–61 °F) on calm, sunny days, though deeper sections remain much colder. By autumn, temperatures drop again toward 9–11 °C (48–52 °F), reflecting the typical mountain climate of North Wales.
Swimming in Llyn Trawsfynydd is officially permitted, though the water remains cold even in summer and can change depth sharply. It is most suitable for experienced open-water swimmers or those wearing wetsuits. The lake’s clean water and scenic backdrop make it popular for kayaking, paddleboarding, and fishing. Safety precautions are advised because the wind can create small waves on open stretches. Surrounding walking and cycling paths offer excellent views of the lake and the nearby peaks of Snowdonia. Other attractions close by include Coed y Brenin Forest Park and the historic village of Trawsfynydd itself.