Lightning is an electrical discharge caused when static electricity builds up between thunderclouds, or thunderclouds and the ground. Lightning strokes carry up to 100 million volts of electricity and leap from cloud to cloud, or cloud to ground and vice versa. Lightning tends to strike higher ground and prominent objects, especially good conductors of electricity such as metal.
Thunder is the noise caused by the explosive expansion of air due to the heat generated by a lightning discharge. Thunder may have a sharp cracking sound when lightning is close by, compared to a rumbling noise produced by more distant strokes.
Because light travels at a faster speed than sound, you can see a lightning bolt before the sound of thunder reaches you.
Lightning may strike several miles/kilometres away from the parent cloud and precautions should be taken even if the thunderstorm is not directly overhead.
