The adaptation to heat arising in daily life was grasped by experiments in a climate chamber. The experiments were composed of +5 degree centigrade load from normal temperature to the subject in the test room during 30 minutes with clothing insulation of 0.37clo and carried out frequently by five young men of 20's from June to October 2004. Based on thermal physiology the term of the adaptation to heat was divided into five intervals; normal, intermittently ascending, continuous, intermittently descending, and normal. The characteristic of the adaptation to heat was found to be that after a short uncomfortable summer, a long comfortable summer will come.
