The photo was taken with a thermal camera, a device that records temperature differences and transforms them into an image.

The image shows a biological pool during an August night. You can see the ladder with stairs. Colors represent temperature classes. Terrestrial vegetation is the coldest, in blue. On the banks you can see the green of the riparian plants and the warm water with a temperature of 26 ºC at 9:45 pm. The wood of the jetty and the stainless steel of the ladder are very cold at this time.

Water needs time to heat up, in other words, it is difficult to store energy in water. This is the main reason for fresh water still throughout spring while air temperatures are already very high. Once water is heated up, it maintains energy well. It is the main reason for an extended bathing season in autumn.

But we must not forget to mention that it is the minimum temperature at night that determines temperature of the water in biological pools. Thus, warm summer nights guarantee high water temperatures. With more cool autumn nights the water loses its warm temperature. Until then, we still have many days of good swimming in which we can enjoy the biological pool. In the south of Portugal, the bathing season easily lasts until beginning of November.

home / news