The typological links between *Thunaraz and Indra are well known and I have discussed these several times on my blogs but what is less well known is the connection between *Thunaraz and Parjanya who may be a separate deity from Indra or perhaps a hypostasis. Like Indra He is referred to in the Rig Veda. According to Wendy Doniger O'Flaherty in her translation of excerpts from the Rig Veda:
"Parjanya, god of fructifying rain, makes Soma and other plants grow."
She also states:
"ultimately Indra is affirmed to be supreme. Indra is also intimately connected with Parjanya the rain-cloud, who is, like Indra, called a bull (5.83) but is also called a cow (7.101).
"Only three hymns are dedicated to Parjanya, who is the personification of the rain-cloud, often represented as a male animal. Closely associated with thunder and lightning, he inspires vegetation and produces fertility in cows, mares, and women. So rich is the abundance with which he responds to the poet's plea that at the end of the hymn he is begged not to send too much rain."
In the first of these free hymns He is personified as a bull, in the second as a cow and in the third as a gale wind.
Like Indra He is said to fight against demons:
"He shatters the trees and slaughters the demons; he strikes terror into every creature with his enormous deadly weapon. Even the sinless man gives way before the god bursting with seed like a bull, when the thundering Parjanya slaughters those who do evil." (Rig Veda 5.83,2, W. Doniger O'Flaherty's translation)
"He smites the trees apart, he slays the demons: all life fears him who wields the mighty weapon. From him exceeding strong fices e'en the guiltless, when thundering Parjanya smites the wicked." (Ralp T.H. Griffith's translation)
Like both *Thunaraz and Indra He drives a chariot:
"O, the power and glory of the chariot of the gale! It breaks things into pieces as it passes by, making a sound like thunder." (Rig Veda 10.168, Donniger O'Flaherty)
"O THE Wind's chariot, O its power and glory! Crashing it goes forth and hath a voice of thunder."(Griffith)
Interestingly Donniger O'Flaherty ascribes this hymn to Parjanya whilst Griffith ascribes it to Vayu! The seed of Parjanya is obviously the life-giving rain.
As well as exhibiting the typical traits of the Thunder God Parjanya is also cognate with the Baltic Perkunas and the Slavic Perun. It is my opinion that He is a much older deity than the more popular and powerful Indra but even at the time of the Rig Veda He is still recognised as a deity but one that is very much in Indra's shadow. His name indicates His great antiquity for He is directly cognate with the original Proto-Indo-European