An icicle is a spike of ice forme when water dripping or falling from another object freezes. Typically, icicles will form when ice or snow is melted by either sunlight or some other heat source (such as heat leaking from the interior of a heated building), and the resulting melted water runs off into an area where the ambient temperature is below the freezing point of water (0°C/32°F), causing the water to refreeze. Over time continued water runoff will cause the icicle to grow. If an icicle grows long enough to touch the ground (or its corresponding ice spike growing up from the ground) then it is called an ice column.