In Meteorology Today - authored by Ahrens - explains that a cloud becomes electrified as hail falls through a region in the cloud of super-cooled droplets and ice crystals. As liquid droplets collide with hailstone, they freeze on contact and release latent heat. This keeps the surface of the hailstone warmer than that of the surrounding ice crystals. When the hailstone comes in contact with an ice crystals, an important phenomenon occurs - electrons flow from the cooler object toward the warmer object.
In spite of the many sources for ideas to write, it's the Holy Qur'an gives me the idea for this article. Awesome!
Sources of facts and other info: Aristotle, Meteorology, Holy Quran, Wikipedia and YouTube for video, Pixabay for photos.