Many companies unavoidably store coals at their stock areas for later usage. Stock fires take place due to long-term stay of these coals at the stock areas and cause serious damages in terms of economy and environment. In order to determine the occurrence conditions of spontaneous combustion of coals due to long-term stay under natural air conditions, an industrial-scale coal stockpile composed of 10 to 18 mm coal grains, having the dimensions of 5 m width, 3 m height, and 10 m length and weighing approximately 120 tons, was formed in a coal stock area of a company using great amounts of coal annually. Recording the temperature values measured at the stockpile, the temperature-time diagrams were plotted. Moreover, the atmospheric effects on the stockpile were investigated by continuously measuring air temperature, air humidity, atmospheric pressure, velocity, and direction of wind, which are some of the parameters affecting the stockpile.