Siting of hazardous facilities such as Nuclear Power Plants requires the investigation of the meteorological and climatological characteristics of the site region to derive extreme values of the meteorological variables to be considered in the design for safety purposes. Meteorological aspects of external hazards to be considered include extreme values of meteorological parameters as well as rarely occurring hazardous meteorological phenomena [1] [2] . The important meteorological characteristics of concern include wind, precipitation, snow, temperature, storm surges [3] [4] and rare meteorological phenomena such as lightning, tornadoes, tropical cyclones.

Lightning is a visible electrical discharge most commonly produced in thunderstorms. Lightning transients exhibit extremely high voltages, currents and current rise rates. Lightning is a significant cause of interruptions or damage in almost every electrical or electronic system that is exposed to thunderstorms, [5] . Damage is usually categorized as either direct or induced (indirect). The extreme electric field created under certain circumstances produces point discharges and can cause breakdown (a conductive path) in all but the most robust of insulators. Once a path has been established for the return stroke, currents of tens to hundreds of kiloamperes flow. It should be noted that lightning is an unpredictable transient phenomenon with characteristics that vary widely from flash to flash and whose measurement is difficult. The hazard assessment for lightning should result in an estimated annual frequency of exceedance for lightning strike for the planned nuclear power plant.

The present study devoted to predict the probability occurring thunderstorms across the North and East coasts of Egypt. Four atmospheric stability indexes are measured for that. These indexes are: K-indics, the Showalter, total totals and the SWEAT [6] . These indexes combine important meteorological parameters of concern to thunderstorms production, to determine its relative probability. Two Egyptian coastal cities have been chosen for the investigation, one on the Northern Mediteranean Sea and the other on Red Sea; El Sallum and Sharm El Sheikh, respectively.

The investigated area comprises two coastal cities in Egypt; Sham El Sheikh and El Sallum. Sharm El Sheikh city is situated on the coastal strip along the Red Sea, which includes the smaller coastal towns of Dahab and Nuweiba as well as the mountainous interior, Saint Catherine’s Monastery and Mount Sinai. Nowadays it is a major touristic hotspot and resort city in Egypt [7] . And Sallum city is on the other hand situated on the Egyptian Mediterranean northwest Coast, along the border with Libya [8] , as shown in Figure 1.

Table 1 and Table 2 [9] [10] , show indicate mean values of the major meteoric conditions of several stations including that are concerned in the studied two cities; Sham El Sheikh and El Sallum.

The atmospheric stability and the thunderstorm vulnerability have been examined in two coastal cities in Egypt; El Sallum at the northwest coast and Shrm El Sheikh at the Red Sea Four meteorological indexes; Showalter Index (SI)) [11] , Total Totals Index (TT), K-index, and Severe Weather SWEAT, have been calculated and functioned for that purpose. Radio soundings [12] are used to obtain vertical profiles of thermodynamic (pressure,