Many omens are found in the natural world. The ancients would observe the behavior of animals, the movements of the clouds during the day and the positions of the stars at night and draw conclusions. Natural Disasters such as earthquakes, floods and hurricanes were thought to be omens of divine discontent with humanity. The ancient Babylonians, Sumerians and Assyrians were especially interested in omens and almost anything that happened was taken as a sign of good or bad fortune.

Omens could also be precognitive dreams and the appearance of banshees, spirits, ghosts, spectral animals, phantom ships and visions. The English Civil War, for example, was predicted by numerous people who claimed to have seen visions of armies battling in the sky.