Is the water cold?
Water can feel cold, cool or warm depending on its temperature, and there is no single answer to whether water is cold: it depends on where the water comes from, the season and the surroundings, and on the person experiencing it. In this article, we look at what is meant by cold and cool water, what affects the temperature of water, and what effects cold water has.
What is meant by cold water?
Water is usually called cold when its temperature is clearly below room temperature (about 20–22 °C), often below 15 °C. Water below about 20 °C is often described more mildly as cool. The limits are subjective, however: different people experience the same temperature in different ways.
Factors that affect water temperature
- Climate and weather: The temperature of the outside air directly affects the temperature of the water. For example, in winter the water in lakes and rivers is usually colder than in summer.
- Water source: Groundwater stays cool all year round because it is protected from the warming effect of the sun; in Finland its temperature is often around 4–10 °C. The temperature of tap water also varies with the season: it is usually warmer in summer and cooler in winter.
- Time of day: In the mornings and evenings, the water can be colder than during the day, when the sun warms it.
- Depth: In deeper layers of water, the water is usually colder than at the surface, because the sun’s heat does not reach as deep.
Effects of cold water
Cold water has many effects on both people and the environment:
- The body: Cold water can feel refreshing, and many athletes use cold water pools for recovery. Long or sudden exposure to very cold water can, however, be a strain on the body or even dangerous, so for example in winter swimming it is wise to be careful and let the body get used to the cold gradually.
- Environment: Water temperature affects aquatic ecosystems, for example the living conditions of fish and other aquatic animals.
- Experience: Whether water feels pleasant or unpleasant depends on personal preferences, the temperature of the surroundings and, for example, whether you have just done something physically strenuous. On a hot day cool water feels refreshing, while on a cold day the same water can feel unpleasant.
Conclusion
Water can be cold or cool for many reasons, depending on its source, the season, the depth and the time of day. How cold it feels is ultimately individual, but groundwater stays cool all year round, while surface waters follow the changes in weather and seasons.
