Spectacular, powerful, and sometimes deadly, lightning (as seen here on the plains east of Boulder, Colorado) is one of the most common weather phenomena. It has been estimated that lightning strikes the earth about 100 times every second. Lightning is generated in cumulonimbus clouds, which have a negative electrical charge at the base and a positive charge at cloud top. Scientists are not yet certain how clouds get these charges, although they know that the charges are carried by water droplets and ice crystals.
