Among these original national gods Jupiter or Jove was the favorite … In the early centuries of Rome he was still a half-impersonal force–the bright expanse of the sky, the light of the sun and moon, a bolt of thunder, or (as Jupiter Pluvius) a shower of fertilizing rain; even Virgil and Horace occasionally use “Jove” as a synonym for rain or sky. In time of drought the richest ladies of Rome walked in barefoot procession up the Capitoline hill to the Temple of Jupiter Tonans–Jove the Thunderer–to pray for rain. Probably his name was a corruption of Diuspater, or Diespiter, Father of the Sky.

–Caesar and Christ, by Will Durant, p. 61

… and when the Romans encountered Zeus, they said, “Hmm, seems to be Jupiter.”