Icicles

Icicles form when the air is around freezing level. The areas not in direct sunlight will be cool and below freezing, while the sun melts ice and snow on more exposed surfaces. The melting water dripping down along edges refreezes in the cool air, forming a column of ice - the icicle. When droplets of melted snow drip down an icicle, they release small amounts of heat as they freeze. Heated air travels upwards and helps slow down the growth of the icicle's top, while the tip is growing rapidly. The water will run down the sides of the formation evenly in a thin film and freeze on the way down. This sort of freezing, thin film of water is what leads to the eventual icicle shape.