The number of heat disorder patients increases according to high temperature and high humidity. Sudden heat raises the risk for heat disorder, however, the first heat spell after rainy season(called 'Tsuyu' in Japan) should be especially taken care for. In 2010 Japan experienced the hottest summer for last 100 years, and during the first heat spell, the ratio of serious patients reached to 4 to 7 percents (normally the ratio varies 0 to 4 percents). And the ratio of elderly patients increased to 60 percents. It reveals that the first and severe heat spell affected especially for elderly people, and their symptom became quite worse than normal situation.