Summanus had a temple at Rome near the Circus Maximus, dedicated at the time of the invasion of Italy by Pyrrhus, king of Epirus (278), when a terracotta image of the god (or of Jupiter himself) on the pediment of the Capitoline temple was struck by lightning and hurled into the river Tiber.
Here sacrifice was offered every year to Summanus on the 20th of June, together with cakes called summanalia baked in the form of a wheel, supposed to be symbolical of the car o the god of the thunderbolt.
The later explanation that Summanus is a contraction from Summus Manium (the greatest of the Manes), and that he is to be identified with Dis Pater, is now generally rejected.