People have looked at the sky from the beginning and their appearance, and one of the most spectacular phenomena that were physically experienced were lightning strikes and lightning falling to the ground.
Brontomancy is the ancient art of divination based on the interpretation of the lightning sound, its direction, duration of thunder and distance from the observer. It was also considered whether the thunder was accompanied by a lightning flash.
The word Brontomancy comes from Greek, and alternatively expressions such as brontoscopy and brontomantia are used. Brontomancy should be considered as one of the forms of Ceraunoscopy.
Many divination methods based on the left and right sides interpret the first as an omen of something bad, while the second as a sign of happiness. It is no different in the case of brontomancy where the thunder on the left was a bad omen but the right symbol of something good. A long and loud bang meant something sinister, and the longer the sound, the worse it was getting ready.
It is interesting that brontomancy was divided by a calendar week. If the storm took place on Tuesdays and Thursdays, people considered it a good trailer promising a large amount of grain and corn. Much more unfortunate was the Monday storm, which indicated the death of a woman, Wednesday indicating the death of a scholar, and Wednesday associated slightly with Monday, for then the harlot was to die, and it is possible that somebloodshed was also to come.
Also Fridays and Saturdays were not happy from the point of view of brontomancy, because Friday meant the murder of a great man, and Saturday – universal death or plague. Once life was much more difficult and more violent, so you can not be surprised by the widespread pessimism of people, which was also visible in other methods of divination practiced in the Middle Ages.
It is enough to add the fact of medieval perception of lightning and thunder as a harbinger of war, flood or death of an important person living nearby.
The Slavs, with particular emphasis on the Russians, practiced the divination of lightning, but Russian clergy banned this practice from around the 14th century.