The term "White Summer" refers to a period of unusually warm weather that occurs during the winter season in certain regions, particularly those located at higher latitudes. This phenomenon is caused by an unusual displacement of the polar jet stream, which allows warmer air from lower latitudes to move northward and replace the cold Arctic air. The term "White Summer" was coined because it often leads to snowfall in areas that are not typically expected to experience such weather conditions during the winter months.