|Practices and beliefs|
In ancient Roman religion, Summanus (Latin: Summānus) was the god of nocturnal thunder, as counterposed to Jupiter, the god of diurnal (daylight) thunder. His precise nature was unclear even to Ovid.
The temple of Summanus was dedicated during the Pyrrhic War c. 278 BCE on June 20. It stood at the west of the Circus Maximus, perhaps on the slope of the Aventine. It seems the temple had been dedicated because the statue of the god which stood on the roof of the temple of Iupiter Capitolinus had been struck by a lightningbolt. Every June 20, the day before the summer solstice, round cakes called summanalia, made of flour, milk and honey and shaped as wheels, were offered to him as a token of propitiation: the wheel might be a solar symbol. Summanus also received a sacrifice of two black oxen or wethers. Dark victims were typically offered to chthonic deities.
Saint Augustine records that in earlier times Summanus had been more exalted than Jupiter, but with the construction of a temple that was more magnificent than that of Summanus, Jupiter became more honored.
Cicero recounts that the clay statue of the god which stood on the roof of the Temple of Jupiter Optimus Maximus was struck by a lightningbolt: its head was nowhere to be seen. The haruspices announced that it had been hurled into the Tiber River, where indeed it was found on the very spot indicated by them.
The temple of Summanus itself was struck by lightning in 197 BCE.
Pliny thought that he was of Etruscan origin, and one of the nine gods of thunder. Varro, however, lists Summanus among gods he considers of Sabine origin, to whom king Titus Tatius dedicated altars (arae) in consequence of a votum. Paulus Diaconus considers him a god of lightning.
The name Summanus may be derived from the Latin sub-manus (cf. mane, Matuta) for "preceding the morning", but was formerly thought to be from Summus Manium "the greatest of the Manes", or sub-, "under" + manus, "hand".
Georges Dumézil has argued that Summanus would represent the uncanny, violent and awe-inspiring element of the gods of the first function, connected to heavenly sovereignty. The double aspect of heavenly sovereign power would be reflected in the dichotomy Varuna-Mitra in Vedic religion and in Rome in the dichotomy Summanus-Dius Fidius. The first gods of these pairs would incarnate the violent, nocturnal, mysterious aspect of sovereignty while the second ones would reflect its reassuring, daylight and legalistic aspect.
According to Martianus Capella, Summanus is another name for Pluto as the "highest" (summus) of the Manes. This identification is taken up by later writers such as Camões ("If in Summanus' gloomy realm / Severest punishment you now endure …")  and Milton, in a simile to describe Satan visiting Rome: "Just so Summanus, wrapped in a smoking whirlwind of blue flame, falls upon people and cities".
Summanus and Mount Summano 
Traditionally Mount Summano (elevation 1291 m.) in the Alps near Vicenza (Veneto, Italy) is considered a site of the cult of god Pluto, Iupiter Summanus and the Manes .
The area was one of the last strongholds of ancient religion in Italy as is shown by the fact that Vicenza had no bishop til 590 CE.
Archeological excavations have found a sanctuary area that dates back to the first Iron Age (9th century BCE) and was continuously active til late antiquity (at least the 4th century CE). The local flora is very peculiar as in ancient times pilgrims used to bring flowers from their native lands.
The mountain top is frequently hit by lightningbolts. The mountain has a deep grotto (named Bocca Lorenza) in which according to a local legend a young shepherdess got lost and disappeared. The story looks to be an adaptation of the myth of Pluto and Proserpina.
The content of this section is adapted from the entry Monte Summano of WP Italian.
Notes and references 
- Paulus Festi epitome p.188 L 2nd.
- "The temple is said to have been dedicated to Summanus, whoever he may be" (quisquis is est, Summano templa feruntur): Ovid, Fasti 6, 731. Translation by James G. Frazer, Loeb Classical Library. Pliny mentions the temple at Natural History 29.57 (= 29.14).
- Ovid fasti VI 729-731; Fasti Esquil., Venus., Amit.: ad XII Kal. Iul.; CIL I 2nd p. 211, 221,243, 320
- Pliny Nat. Hist. XXIX 14; Livy Periochae XIV. For dedication year, see Orlin, Eric M., "Foreign Cults in Republican Rome: Rethinking the Pomerial Rule", Memoirs of the American Academy in Rome, Vol. 47 (2002), p. 5.
- S. Ball Platner, T. Ashby A Topographical Dictionary of Ancient Rome Baltimore 1928 p. 408, citing Cicero de Div. I 10; Livy Periochae XIV; Iordanes I 2, 14-15; 98-100
- Festus p.557 L
- John Scheid, "Sacrifices for Gods and Ancestors", in A Companion to Roman Religion (Blackwell, 2007), p. 264; Raffaele Pettazzoni, "The Wheel in the Ritual Symbolism of Some Indo-European Peoples," in Essays on the History of Religions (Brill, 1967), p. 107.
- Augustine, City of God IV 23
- Cicero De Divinatione I 10
- Livy AUC XXXII 29, 1
- Natural History 2.53 (alternative numbering 52 or 138): "The Tuscan books inform us, that there are nine Gods who discharge thunder-storms, that there are eleven different kinds of them, and that three of them are darted out by Jupiter. Of these the Romans retained only two, ascribing the diurnal kind to Jupiter, and the nocturnal to Summanus; this latter kind being more rare, in consequence of the heavens being colder" (Tuscorum litterae novem deos emittere fulmina existimant, eaque esse undecim generum; Iovem enim trina iaculari. Romani duo tantum ex iis servavere, diurna attribuentes Iovi, nocturna Summano, rariora sane eadem de causa frigidioris caeli). English translation by [[John Bostock (physician)|]], via Perseus Digital Library.
- Varro Lingua Latina V 74.
- Entry on Dium above.
- Myth et epopée vol. III part 2 chapt. 3; Mitra-Varuna: essai sur deux representations indoeuropeennes de la souverainetè Paris 1948 2nd; La religion romaine archaïque Paris 1974; It. tr. Milano 1977 p. 184
- Martianus Capella, De nuptiis 2.164.
- Os Lusíadas, IV, 33, translated as The Lusiad by Thomas Moore Musgrave (1826).
- In the Latin poem "In Quintum Novembris" (lines 23–24): Talibus infestat populos Summanus et urbes / cinctus caeruleae fumanti turbine flammae.
- Lucio Puttin Monte Summano: storia, arte e tradizioni Schio, 1977.