Lake
Silfra Fissure
Silfra Fissure water temperature is currently Ice Risk. Near-freezing water. Extreme cold shock risk. Expert preparation required. Located in the Sub-Arctic climate zone, it is currently spring. Air has averaged 1°C over recent weeks. Temperatures are at or near freezing. Dangerous conditions without cold water training and appropriate equipment.
Last updated:
Ice Risk
Near-freezing water. Extreme cold shock risk. Expert preparation required.
Air has averaged 1°C over recent weeks. Temperatures are at or near freezing. Dangerous conditions without cold water training and appropriate equipment.
Lakes warm slowly in spring. Water is often colder than air conditions suggest.
Lake size
Larger lakes warm and cool slowly. Ponds respond quickly to air temperature.
Temperatures have been near freezing. There may be ice.
Is this lake currently ice-covered?
Swum here recently?
Community temperature reports are the most reliable local data.
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7-Day Forecast
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3.3°C
High 6.8° / Low -0.3°
Very cold air, water will feel brisk
-0.1°C
54cm depth
Ground is cold at depth, low baseline water temperature
Weak
143 W/m²
Overcast skies, limited surface warming
8 km/h
NE, gusts 19
Calm conditions, sheltered water likely
2.5°C
Feels like wet
Cold exit conditions. Wet skin and wind will chill you rapidly. Pre-lay your clothes.
50.5 mm
7-day total
51mm of rain in the last 7 days. Lake inflows may have cooled and clouded the water.
Model estimates. Always assess the water yourself before entering.
Frequently asked questions
How is the lake water temperature estimated?
Lake temperature is estimated using exponential smoothing of 60 days of air temperature data, based on Kettle et al. (2004). The algorithm accounts for lake thermal mass. Larger lakes respond more slowly to air temperature changes. This is not a direct measurement; accuracy is approximately plus or minus 2 to 3 degrees C.
What do the temperature categories mean?
Each category covers a 4 degree C band: Warm (20 degrees C or above, no wetsuit needed), Comfortable (16 to 20 degrees C, most swimmers fine), Cool (12 to 16 degrees C, wetsuit optional), Cold (8 to 12 degrees C, wetsuit recommended), Very Cold (4 to 8 degrees C, wetsuit essential), Ice Risk (below 4 degrees C, experienced swimmers only).
What is the geographic zone?
The zone is derived from the lake's latitude and altitude. It reflects the climate regime: temperate zones have the highest model accuracy; alpine and equatorial highland zones have reduced accuracy due to solar heating effects not fully captured by air temperature data alone.
What is the swimmer exit temperature?
The exit temperature uses the Steadman (1984) apparent temperature formula, which accounts for wind speed and humidity on wet skin. Exiting water in wind with wet skin causes significantly faster heat loss than the air temperature alone suggests, especially at speeds above 20 km/h.