Why is the water at 30 degrees a little cold and the weather at 30 degrees very hot?

This is very simple, because the weather around 30 degrees in summer means that the temperature of the whole environment is around 30 degrees. At this time, the temperature is close to the human body temperature, and the body temperature will be released slowly, so you will feel very hot. If you take off your clothes, it might be cooler. If the ambient temperature is lower than 30 degrees, water will absorb part of the ambient temperature, the water temperature will drop, and water molecules will move from high temperature to low temperature. Besides, our temperature is about 36 degrees Celsius. After taking a shower, we took off our clothes. The water temperature is 30 degrees Celsius, which is lower than our body temperature, so we feel the water is cold. If the water temperature is above 40 degrees, you won't feel cold. This is a physical phenomenon, convection heat conduction.

Let it catch on. Thermal convection: thermal convection refers to the heat transfer mode in which hot and cold fluids are mixed due to the macroscopic movement of fluids. This heat transfer only occurs in liquids and gases. Due to the irregular thermal motion of molecules in fluid, convection is inevitably accompanied by a large number of heat transfer phenomena in real life. For example, we boil water with fire, roast mutton kebabs with charcoal fire, roast our hands with fire when we are cold, warm our mattresses and so on. Let children learn physics knowledge when they grow up. Learning physics can explain many natural phenomena.

It depends on the bathing season and indoor temperature of the child. As the saying goes, there is not a day in June when the temperature of bath water at 30 degrees is lower than the normal temperature of human body. Children and the elderly will feel very uncomfortable. Of course, they may even cause a cold. Water is flowing, so is air, but compared with water, air is very small.

Therefore, if we are at 30℃, we will feel hot, because our skin is cooling, but the air flow is weak, so the efficiency of the cooling system is not very high, so the heat generated by our body cannot be released, and we will feel hot. When we take a bath, we still feel very cold even in water at 40 degrees Celsius. Although the water temperature is higher than that of human body, the heat dissipation efficiency of human skin is very fast due to the flow of water. The heat generated by our bodies is less than the heat absorbed by water, which makes us feel very cold.