In Mesopotamian religions, weather god, ruling in particular rain and storm. His qualities were both advantageous as well as destructive. Even his destructive side could be positive, if turned against one's enemies.
The consort of Adad was Shala or Shalash, the goddess of grain. His parents were the moon god Nanna/Sin and goddess Ningal. He was brother of the sun god Utu/Shamash and the goddess of fertility, Inanna/Ishtar. Competing myths make him either the son of Enlil; or of Anu.
His symbol was the cypress, and his sacred number was 6. Adad could be symbolized by a bull, and in some cases, a lion.
Adad could be associated with Amurru in Amoritic religion, as well as Hadad in Semitic religion. At long periods, there seems not to have been any cult centres uniquely dedicated to him.
In Sumerian religion, his name is Ishkur. He was not an important god the way he would become from the Akkadian period. Also, his qualities were not unique, other and already important gods, like Enlil and Ninurta, ruled the storm.
In Akkadian religion, the name changes to Adad. Another name used was Ramman, meaning "The Thunderer".
The explanation to why he emerged as an important god in Akkad is that the phenomenons of storm and rain were far more common, and important, in the Akkadian heartland, subject to the mountains.
In Babylonian religion, both Adad and Ishkur were used. The Babylonian cult centre was Karkara.
Similar to Babylonian religion, Assyrian religion used both Adad and Ishkur. He was worshipped alongside Ahu in Ashur.
With the Assyrians, the warrior aspects of Adad were developed. He is sometimes represented with a horned helmet holding a fork-shaped lightning and thunderbolt.
Together with Shamash, he was a god of oracles and divination.