World temperature has increased in recent history and this trend is likely to continue in the near future. Accompanying this change, there has been an increase in extreme weather events, often leading to devastating demographic, economic, environmental and social impacts. Studies of impacts of extreme weather conditions, including the health impact of very hot weathers or heatwaves, have also increased considerably in recent years. Despite that investigations using detailed data collected from less developed countries over a relatively long-period are difficult to find. This study analyses mortality and weather condition data gathered from Taiwan over recent decades. It shows that in the 1970s, more extreme temperature was very closely related to the increase in daily mortality, and marked mortality peaks were frequently observed in winter and summer. While old people and those with cardiovascular diseases tended to be more vulnerable to cold weather, the risk of mortality among children and young people increased notably and many of them died of injuries and poisoning in hot summer. It is particular noteworthy that the temperature-mortality relationship has not been constant, but gone through significant changes in recent decades. One of the major changes has been the disappearance of major summer mortality peaks.