Summanus: Celebrating Jupiter’s Forgotten Dark “Twin”

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20th June was the day of Summanus, the god of night-lightning. Photo courtesy of C Clarke, image by Saperaud.

The 20th of June is the commemoration of the enshrinement of Summanus, the god of nocturnal lightning, and one of Rome’s oldest gods.

At one time, Summanus was more popular than Jupiter. But by the time of the Emperor Augustus, he slipped into being a nearly-forgotten deity whose past significance was lost, and who eventually only survived in memory as a dark, underworld deity.

So who was Summanus? And why did the Romans venerate and then forget him?

The Origins of Summanus

The origin of Summanus’ name is obscure, there are many theories on the subject.

The name may come from the Latin preposition ‘sub’ combined with the noun ‘mane’ meaning ‘before the morning’ — which is logical as Summanus was the god of night-time lightning.

According to Varro, Romans adopted Summanus at the time of Romulus. The Roman King and his Sabine ally, Titus Tatius, each instituted new cults. Romulus introduced the cult of Jupiter while Tatius “vowed altars to Ops, Flora, Vediovis and Saturn, Sun, Moon, Vulcan and Summamis, and likewise to Lariinda, Terminus, Quirinus, Vertumnus, the Lares, Diana and Lucina.”

Pliny in his Natural History mentions that the Etruscans recognized nine gods of thunder, of which Summanus was only one — suggesting the god’s origins were Etruscan. But Summanus could have been older still.

Near Veneto in the Italian Alps is a Mount Summano, which is associated with the cult of Summanus. This area was just on the edge of Etruscan cultural influence, suggesting that Summanus’s status was impressive enough for the Etruscan’s adopted the god from another people.

But by the fifth century AD, people believed that his name meant something else. A writer of the period, Martianus Capella, believed the god’s name derived from ‘summus manium’ — ‘highest of the Manes,’ the Roman spirits of the dead and also gods of the underworld. This led to an association between Summanus and Pluto, the chief god of the underworld.

But originally, Summanus was associated with a very different god of the Roman pantheon.

Summanus: Jupiter’s Dark Twin

According to Pliny, of the nine Etruscan lightening gods, the Romans kept only two: Summanus and Jupiter:

They attribute daytime thunderbolts to Jupiter,” stated the first century AD writer in his Natural History,” and ones at night to Summanus.”

This description seems to suggest that at one point in their history, Summanus was the equal-and opposite aspect of Jupiter. It is reinforced by an inscription cited in Religions of Rome: A Sourcebook from 224 AD describing the sacrifices offered to propitiate the gods after lightning destroyed several trees from the grove of Dea Dis just outside Rome. The Romans offered Jupiter 2 ordinary wethers, or castrated rams. They offered Summanus was offered an equal number of the same beast — except, as befitted a nighttime god, his wethers were black.

Summanus’s Temple and Cult


The temple of Summanus was constructed somewhere in the vicinity of the Circus Maximus. Image by Ursus.

Little evidence remains of Summanus’s cult in Rome, but he must have been held in some regard and importance, as a temple was dedicated to him on the 20th June sometime between 275-278 BC. The temple, which was located near the Circus Maximus, was dedicated sometime during the war with Pyrrhus – not because of the conflict – but because, according to Fowler, lightening destroyed a statue on the temple of Jupiter one night.

This seems to have convinced the Roman’s of the strength of Summanus and not only did he gain his own temple but every 20th June, he was propitiated with summanalia round cakes made of flour, milk and honey.

Summanus: The Forgotten God

In fact, some evidence suggests that for some, Summanus may have been held in higher regard than Jupiter himself. St Augustine states that:

The ancient romans paid greater honours to I know not what Summanus, to whom they attributed nocturnal thunderbolts, than to Jupiter.”

But he then adds:

“… But after a famous and conspicuous temple had been built to Jupiter, owing to the dignity of the building, the multitude resorted to him in so great numbers that scarce one can be found who remembers even to have read the name of Summanus.”

This seems to tie in with events from 197 BC described by Livy. Not only was a new temple to Jupiter constructed but Summanus’s own temple was struck by lightening. It may be a lightening strike on Summanus’s shrine that suggested to the Roman people that the nocturnal god’s power was waning. On the other hand, Jupiter was also head of the Roman pantheon — a position strengthened by his association with the Greek Zeus.

From then onwards, Summanus seems to have been on the wane. By the early imperial period, he had become sufficiently obscure for Ovid to mark the 20th June as dedicated to “Summanus, whoever he is.”

Temple of Jupiter

The construction of a new temple of Jupiter marked the downward spiral in Summanus’s fortunes. Art by Hercule Louis Catenacci and Charles Laplante, courtesy of the NYPL Digital Gallery.

Jupiter Summanus: Nocturnal Aspect of Another God?

 If he was remembered at all, Summanus only survived as an adjunct trait of Jupiter. Later inscriptions mention, Jupiter Summanus – a nocturnal aspect of the Roman lightening god instead of a separate deity in his own right.

But Summanus survived in history with a darker reputation. In the sixteenth century, Martianus Capella’s association between Summanus and Pluto seems to have led the Portuguese poet Cameoes to associate Summanus with hell, when he describes how:

“If in Summanus’ gloomy realm / Severest punishment you now endure”

Thunder God and the Cycle of Life

This seems a sad end for a thunder god. But even if the function of Summanus as a god of lightening had mutated to an association with the underworld deities in late antiquity, that does not mean he deserved an evil reputation.

For the chthonic (subterranean) deities were originally linked to the cycle of life. The dead were returned to the ground but the ground also gave life to plants and crops. So. even if many of the true attributes of Summanus are forgotten, his reputation does not deserve to survive in such a gloomy fashion.

© Copyright 2014 Natasha Sheldon, All rights Reserved. Written For: Decoded Past

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