Meteorology in Aratus’ Phaenomena ^†

Abstract

Aratus’ poem Phaenomena, and particularly its second part commonly known as Diosemeia (Signs from Zeus), offers a compelling blend of poetic narrative and proto-scientific observation. Composed in the 3rd century B.C., the work reflects the Hellenistic interest in systematizing knowledge of the natural world through both literary and empirical means. Within its verses, meteorological phenomena such as clouds, rain, hail, winds, and atmospheric changes are not merely described but interpreted through a cosmological lens that reflects the worldview of the era. Aratus Solensis employs a poetic language that transforms everyday weather into a meaningful sequence of signs tied to divine order and celestial cycles providing in that way a kind of classified weather prognostics.

1. Introduction

Aratus (315 B.C.–240 B.C.), from Soli in Cilicia, Asia Minor, in his works Phaenomena and Diosemeia, combines earlier and contemporary views on astronomy and weather prediction, presenting in verse the work of the renowned astronomer Eudoxus of Cnidus. His poetry is didactic in nature, addressing every person while retaining scientific grounding. His work was influenced mainly by Hesiod (Works and Days) and Theophrastus (About Signs, etc.).

The first (astronomical) part is a marvelous description of the celestial sphere, its constellations, and the corresponding mythology. The second (meteorological) part, Diosemeia (Signs from Zeus), refers to the observations of weather phenomena available up to that time. It is worth noting that in antiquity, celestial phenomena were attributed by our ancestors to the intervention of gods, and that the geocentric system prevailed, especially as developed by Aristotle [1].

2. Materials and Methods

This study is based on the original text of Aratus in Ancient Greek, while for the English language, the translation by A.W. and G.R. Mair (Loeb Classical Library, London, 1921 (https://www.astrologicon.org/aratus/aratus-phaenomena-diosemeia.html (accessed on 29 June 2025)) was used combined with J. Martin’s and D. Kidd’s studies [2,3,4]. We also included commentary by Theon from Alexandria and other ancient Greek and Latin authors in their corresponding works. In this way, the scientific interpretation and significance of the phenomena of our interest were evaluated in the best possible manner.

Although stars have no relation to the meteorological phenomena of the Earth, we can make use of our many years of experience, which begins with the Orphic hymns, in the simultaneous variation in celestial and weather-related events. In his artistic process of the overall gradual descent from the North pole to the ground level, the poet successfully speaks of various phenomena that simultaneously appear on different scales, large and small, and on different levels, astronomical and meteorological [5].

In the projection of the solar movement (Figure 1), the tilt (obliquity) of the Earth’s rotation axis is included. The Earth’s tilt is responsible for the appearance of the four seasons in a year as well as for the existence of the climatic zones, according to Aristotle.

The sun also shows a slowing in its apparent movement by 50.28 arcseconds per year, so over the years it appears to project earlier onto the corresponding zodiac constellations. This is due to the precession of the Earth’s rotation axis, with a periodicity of 25,800 years (Figure 2), which also changes the orientation point of the North (ζ Draconis, the Pole Star of Ursa Minor, Vega of Lyra).

3. Results

Indicatively, we mention that in the Phaenomena (first part), the projected-apparent orbit of the solar disk through the zodiacal constellations circle determines the duration of the terrestrial year, the beginning and duration of the four seasons, the estimation of distances and time intervals, as well as the appearance of recurring—periodic weather phenomena, such as the annual summer winds-etesian, which blow strongly when the sun passes through the constellations of Cancer, Leo, and Virgo observed at the mid-geographical latitudes of the Mediterranean. The etesian winds prevail after the summer solstice and after the concurrent rising of Sirius (α CMa), the brighter star of Great Dog (Canis Major) constellation, and the Sun [6].

In May, the Pleiades open star cluster is typically visible in the predawn sky, particularly in the northeastern direction. The Pleiades (Messier list, M45), in the constellation of Taurus right of Orion, of which seven stars are visible to the naked eye, have been traditionally used to determine the seasons of the year, as well as guiding the farming, livestock and navigation activities. Its rising in May, just before sunrise, marks the beginning of the warm period lasting until autumn, when its rising occurs in the east just after sunset. Its setting in the eastern sky just before sunrise signals the beginning of the sowing season.

In late January and February, in the not particularly bright constellation of Cancer (the southern shell), the misty open star cluster of the Manger (Beehive, M44) is at the zenith. It is accompanied by two stars, the Ashes at the northern and southern edges of the cluster. They are easily distinguishable, as there are no very bright stars in that region of the sky. When the Manger becomes invisible, it is considered a sign of imminent short-term bad weather. If one of the two Ashes appears faint, a northern or southern wind will blow, accompanied by impending rain. Furthermore, if the Manger becomes dark and misty, it signifies the approach of severe weather (vv. 892–908).

The southern semi circumpolar constellation Altar, directly below Scorpius, is visible in the Northern Hemisphere for no more than eight hours during the nights of June and at latitude 22° N. If the stars north of Altar are obscured by clouds, inclement weather is expected, accompanied by southerly winds, which hinder maritime navigation. Conversely, if the neighboring constellation Centaurus appears cloudy after its rising while Altar remains clear, leads to the onset of the southeast wind Euros [7].

Diosemeia (second part), could stand as an empirical tool for weather forecasting, both on short-term and long-term scales, which is based on observations of celestial bodies (Moon and Sun), behaviors of domestic and wild animals, insects, and plants (

Table 1. Indicative Weather Signs in Aratus with Current Scientific Interpretation.

Weather Sign and Aratus’ vv. Category	Aratus’ Description	Scientific Interpretation
Ring around the Moon (811–817)	Rain/Wind	Ice crystals in cirrostratus; warm front likely, rain possible
Red moon (796–798)	Storm/Wind	Horizon light diffusion from moisture/dust; high humidity
Clear bright moon (783–784)	Good weather	Stationary anticyclonic conditions
Low fast clouds (845–847)	Storm	Strong upper-level winds; frontal change likely
Clouds dissolve early in the morning (848–850)	Fair weather	Night humidity drop; stable inversion
Morning north wind (886–888)	Clear day	Cold, dry northern air
Sudden south wind (888–889)	Rain	Warm, moist air; pre-frontal instability
Low bird flight (918–919)	Rain	Pressure drop; humidity rise; insect/bird behavior
Squashed sheep (1068–1070)	Bad weather	Temp/pressure drop; humidity rise; animal behavior change
Blond bees stay in hive (1028–1030)	Wild storm	Unstable air; pressure shift; animal sensitivity
Swelling sea/moaning of the mountain crests (909–912)	Wind/Storm	High humidity; low sunlight; rain risk
Cloud lengthwise resting on the mountain peaks (920)	Humidity/Rain	High humidity; low sunlight
Withered petals floating (921–924)	Wind	Local pressure changes; breeze onset

).

According to the data provided in Table 1, current scientific understanding interprets the empirical observations collected by Aratus [8] as follows:

(a) Quite a few weather prognostics depend on the phases and colors of the Moon, especially during the third and fourth day after the new moon. “If the Moon is thin and clear on the third day, fair weather will come; but if it is hazy and reddish, it foretells wind”. The appearance of a halo around the Moon and the diffusion of its light implies the presence of water droplets and dust in the Earth’s atmosphere, with an increased likelihood of cloud formation and rain. “If the Moon is surrounded by a single thin ring, it is a sign of calm weather; if by two, it foretells winter; and if there is a third, a closer ring, the month will not only be heavy but even harsher”. (783–797), The red moon appears during a total lunar eclipse interpreted by refraction, diffraction and reflection theory. It could also be explained through Mie or Rayleigh scattering depending on atmospheric constituents’ size (λ_red = 6 25 μm).

(b) The sunrise and sunset, as well as each different appearance of the sun during its daily course in the sky, were considered by the ancient Greeks as signs for weather prognostics (819–891).

“Nor are dark halos near the Sun signs of fair weather: when nearer the Sun and dark without relief, they portend greater storms; if there are two rings, they will herald tempests fiercer still” (Figure 3). The reflectivity and color of sunlight on clouds during sunrise and sunset reveal the arrival of bad weather with winds. “The large rings that girdle the sun do not indicate good weather, when the sun rises or sets, and the clouds called parhelia become red on the side of the south and the north—there will definitely be a downpour”. “Parhelia” refers to the reflection of the Sun on the clouds seen close to the sun.

(c) Careful study of change in animal behavior and nature delivers weather prognostics:

When the heron comes from the sea to the land, crying loudly, then the sea, due to the rage of the wind, will be stormy; and if the seagulls fly in flocks during good weather, they fly against the wind that is about to blow.

Another sign that winds will come is when flowers fall from the plants, along with the fluff of white thistles, floating back and forth across the open sea.

Bad weather will come when lake or sea birds dive into the waters without pause, or when the tormented breed of frogs—which are prey to snakes—croak at the edge of the water, or when the turtle-dove sings alone from dawn.

Before the rain falls, oxen sense it and raise their heads high toward the sky, and on the walls crawl many-legged worms called Iuli, along with other slow-moving worms that are called “intestines of the black Earth”.

A sign of rain is also the hens that have been mounted by the rooster, which begin to pluck their feathers and call out with a voice that resembles the sound of a drop of water falling into water. All kinds of crows and families of jackdaws, when the rains of Zeus approach, also give signs by gathering in large numbers and crying out like hawks.

Rain is also foretold by the frenzy with which flies bite and seek to drink blood, as well as by the charcoal that forms on the wick of oil lamps that burn through the whole night, and the wonderful and unusual movement of their flames, which fall here and there like bubbles.

Calm weather is to be expected when dark clouds spread under the foothills of tall mountains, while their peaks remain uncovered.

Fair weather is to be expected when, on the wide-open sea, the cloud appears low and does not rise above the horizon, resembling a raised rock above the sea.

An infallible sign of severe winter is the crow—which is said to live as long as nine human generations—when it cries out with long wailing sounds during the night.

There are no signs of fair weather when, during moments of complete stillness, light fabrics stir as if wind is blowing, or when the flames of oil lamps flicker more intensely, or when the lamps and fire are difficult to light.

When the holly (commonly known as yew, a type of holm oak) is heavily laden with fruit, it foretells a long and harsh winter. The same is true for the black mastic buds, as well as the flowering of the squill (wild onion).

When in autumn, before the setting of the Pleiades, wasps gather in large groups, we can assume that the coming winter will be proportional to the number of wasp clusters.

If goats, sheep, and boars mate late, then the coming winter will be mild.

A stormy winter will come at the setting of the Pleiades if oxen and rams strike the earth with their horns and raise their heads against the northern wind.

Shepherds and ploughmen also learn from the oxen whether a harsh winter is coming, when the oxen turn their heads and lick the nails of their hind legs with their tongues, or when they fall down and lie on their right side. At such times, ploughing must be postponed, and the farmer knows this.

When the wolf howls alone in the wilderness or seeks shelter in inhabited areas—when it should instead be hiding—then expect great bad weather within three days.

If a dog digs the earth with both front legs, it senses bad weather coming.

4. Discussion

However, there are also long-term observations which do not lead to reliable forecasts—such as the appearance of comets or the entry of meteors into the atmosphere—which are not related to changes in the weather. The combination of two or more empirical observations, as Aratus himself emphasizes in concluding his work, constitutes reinforced indications for weather prediction, especially for those engaged in farming or seafaring, when they carefully observe these behaviors and how consistently and frequently they occur. “A good rule it is to look for sign confirming sign. When two signs point the same way, forecast with hope; when three, with confidence … Study all the signs together throughout the year and never shall thy forecast of the weather be a random guess (vv. 1144–1145, 1154–1155)”. Thus, we stand at the border between folk meteorology and preliminary scientific reasoning—without excluding scientific logic in many of the well-studied cases of prognostics.

5. Conclusions

Aratus’ poem, notable for its emphasis on weather prognostics, draws from earlier sources, particularly the work of Eudoxus, to present a range of observational techniques, including the study of stellar risings and settings, lunar phases, and animal behavior. These are interwoven with meteorological insights to form an early system of forecasting. The detailed cataloging of signs and their associated weather outcomes reveals an empirical methodology, albeit one embedded within a mythopoetic framework. Thus, Phaenomena stands as an important text not only in the history of literature but also in the development of ancient meteorological thought. This analysis highlights how Aratus’ work bridges the realms of science, religion, and poetry, offering modern readers a window into the complex ways ancient societies understood and interacted with the natural environment.