Ancient weather calendars

The economy of the ancient Mediterranean world was agriculturally-based. Given the importance of weather to agriculture, it should not be surprising that there was a good deal of interest in the explanation and prediction of weather in the ancient world. Over what was probably a lengthy period of time and through shared effort and cooperation, ancient people (perhaps farmers themselves) determined an astronomical calendar to guide agricultural activities through the course of the year. Hesiod's poem the Works and Days contains, in the final section, something of a farmers' almanac in verse form, with instructions on when to do what, with some technical advice thrown in.; the poet was very likely here sharing the fruits of collective labour and experience. In some cases, the poet indicates that astronomical events can be associated with specific weather events. So, for example, 'when the Pleiades plunge into the misty sea to escape Orion's rude strength, then truly gales of all kinds rage' (619 ff.; at the end of October or the beginning of November); and 'fifty days after the solstice ... the season of wearisome heat is come to end' (663 f.).

It may be argued that the Works and Days stands at the beginning of a special tradition of Greek and Roman calendars, which relate astronomical phenomena to weather.

In the early part of the twentieth century, fragments of two stone inscriptions were excavated at Miletus (in present-day Turkey). One of these was dated to the late second, the other to the early first century B.C. It was recognised that these stone inscriptions were a sort of calendar, known in Greek as a parapegma (plural=parapegmata). It seems that originally the term parapegma, which means 'something on which you fix something next to something else', described a stone calendar that was displayed for public use. The parapegma was inscribed with a list of star phases and corresponding weather predictions; the term was later applied to purely written forms of such calendars, or almanacs. The stone parapegma had holes beside the inscription, in which a peg could be inserted next to the appropriate day. The peg was placed in the hole next to the day named in the calendar and holes were provided in order to count out each day, so that one would not lose the place in the month.

The parapegma may have been the invention of Meton and Euctemon, who worked in 5th century BC Athens and were particularly interested in calendars. Both stone inscriptions and written examples of the parapegma tradition survive, but prior to the discovery of the stone fragments at Miletus, only a written form of parapegma calendar was known. The second century AD Alexandrian astronomer Claudius Ptolemy included a such a calendar in his work known as the Phases of the Fixed Stars and Collection of Weather Signs. Ptolemy's Phases is clearly part of the traditional group of texts that relate astronomical phenomena to weather, while introducing a few innovations (for example, concentrating on first and second magnitude stars, rather than constellations). The Phases is also an important source of information about the parapegma tradition, providing information about Ptolemy's predecessors. This is one of the particularly interesting features of these calendars: names of earlier authorities are listed. That such calendars were produced over such a long period of time is striking, and indicative of their perceived continuing value.