This paper studies interdecadal variations of heat waves and sultry weather (HW&SW) in Beijing City by using climatological data gathered from 1940-2000.In general, HW&SW decreased during the 1940s-1970s and increased during the 1970s-1990s.Although variation trends in the number of HW&SW days coincide with air temperature variations, the greatest number of HW&SW days occurred during the 1940s rather than during the much hotter 1990s (which had an average 1.0°C higher air tem-perature than during the 1940s)...