The purpose of this study was to ascertain the actual conditions of the thermal environment and the symptoms of patient and staff (nurses and nurses' aides) during winter in a hospital. We measured the ambient temperature and humidity in sickrooms, nurse stations, and corridors. The subjects included 36 patients and 45 staff members. The existence of low humidity environments (relative humidity was less than 40%) in a hospital during winter was confirmed, and the levels of low humidity reached those known to promote the spread of influenza viruses. Thermal comfort of patients was not directly connected to the low humidity in sickrooms. However, 54.9% and 73.4% of patients were conscious of itchy skin and thirst, respectively. The majority of the staff members were working with itchy skin and thirst. These results suggested that extreme low humidity in a hospital during winter presents problem that should be solved quickly.