Although there is no standard definition of heat wave, it is generally defined as uncomfortably hot and humid weather conditions, prolonged for more than three days. Since comfort level may vary depending on the local conditions and regular practice, the threshold of a heat wave event should be defined according to these familiarities. Heat waves are also classified, as extreme events such as heavy rainfall, flood, and droughts. Although these events occur rarely their impact can be substantial. Depending on their severity and duration, heat waves can be a deadly threat on human health and on ecosystems. The recent IPCC report AR5 (2013) emphasizes that the magnitude, frequency, and the duration of heat waves may increase depending on the local effects due to the climate change. Therefore, the aim of this study is to determine heat wave events occurred over Turkey and categorize them in terms of their frequency, duration and intensity. Daily maximum temperature observations are used for the period between 1960 and 2013 at 238 stations. 90 th percentile of the maximum temperatures between 1970 and 2000 at each station is used as a threshold value to define the hot day, and if the temperatures continue to stay above the defined threshold for at least three days, it is called as heat wave. General tendency of the heat waves in terms of frequency and duration are investigated for last 53 years. For each heat wave category, the atmospheric conditions leading to the heat waves are explored by analyzing geopotential height, temperature, wind and specific humidity patterns at the pressure levels of 1000 hPa, 850hPa and 500hPa of ERA interim re-analysis data.