Why don't people feel hot when the water temperature is 30 degrees, but people feel very hot when the weather is 30 degrees?

Because water has large specific heat and good heat transfer performance, it can quickly dissipate the heat on the surface of human body, so people can't feel the heat in water at 30 degrees.

In air, because the specific heat of air is small, the heat dissipation performance of air is poor, and the heat generated on the body surface cannot be dissipated quickly, so people will feel quite hot if they are in windless air at 30 degrees. But if the air flows and accelerates heat dissipation, it won't be too hot.