Siting of hazardous facilities such as Nuclear power plants requires the investigation of the meteorological and climatologically of the site region to derive extreme values of the meteorological variables to be considered in the design for safety purposes. Not only normally occurring meteorological conditions but also extremely rare events are considered. The present work is devoted to predict the likelihood of the Thunderstorm which is one of the rare events of concern for plant safety. Four atmospheric stability indices such as K-indices, the Showalter-indices, total totalsindices and the SWEAT-indices have been used for that. These function of meteorological parameters such as temperature, wind speed, wind direction and dew point at levels of pressure at 500, 700 and 850 hpa to predict the thunderstorm probability. Two Egyptian coastal sities have been chosen for the investigation, one on the Mediterranean Sea and the other on Red Sea; El Sallum and Sharm El Sheikh. The results show that the probability of thunderstorm occurred within the months January and February during 1989-2003, where the maximum value of SI, K, TT and