The 4.2 kiloyear BP aridification event is one of the most severe climatic events of the Holocene period in terms of impact on cultural upheaval.

Starting in ≈2200 BCE, it probably lasts the entire 22nd century BCE.

It is very likely that it is the cause of the collapse of the Old Kingdom in Egypt as well as the Akkadian Empire in Mesopotamia.

The drought may have also initiated southeastward habitat tracking within the Harappan cultural domain.A phase of intense aridity in ≈4.2 ka BP is well recorded across North Africa, the Near East, the Red Sea, the Arabian peninsula, the Indian subcontinent, and even midcontinental North America.

Glaciers throughout the mountain ranges of western Canada advance at about this time.

Evidence has also been found in an Italian cave flowstone, and in Andean glacier ice.

The onset of the aridification in Mesopotamia near 4100 B.P also coincided with a cooling event in the North Atlantic, known as Bond event 3.