“At times when it varies between hot and cold on the same day, one must expect the illness of autumn.”

Ἐν τῇσιν ὥρῃσιν, ὅταν τῆς αὐτῆς ἡμέρης ὁτὲ μὲν θάλπος, ὁτὲ δὲ ψῦχος γένηται, φθινοπωρινὰ τὰ νουσήματα προσδέχεσθαι χρή.

Hippocrates, Aphorisms III 4, IV 483 Littré

“When it comes to the weather in late autumn, one must be extremely cautious, since it is variable. Therefore, you mustn’t go walking around barefoot in the early morning and the afternoon, and you mustn’t jump into cold water naked. You also mustn’t go harvesting crops without your tunic on, even if you think the cold air is pleasant and gratifying—it is so difficult to prepare for bad weather, especially when the damage slips in with what seems pleasant. Stay away from the cool breezes coming off of rivers and lakes—they not only cool you down, but they also moisten your dispositions. And make sure to guard against rich foods, like thick and astringent new wines, crackers made from very fine flour, dates, raisins, eggs, snails, grape hyacinths, very meaty fish, sliced sausages, lamb, and mutton. Also, don’t forget to get a bit of exercise.”

τὰς δ’ ἐν τῷ μετοπώρῳ πολλῷ μᾶλλον δεῖ εὐλαβεῖσθαι· γίνονται γὰρ μετ’ ἀνωμαλίας. δεῖ τοίνυν μήτε ἀνυποδέτους περὶ τὸν ὄρθρον καὶ τὸ δείλης διάγειν μήτε ἀσκέπως εἰς ψυχρὸν ὕδωρ ἐμβαίνειν μήτε ἀχίτωνας θερίζοντας διὰ τὸ κεχαρισμένον καὶ ἡδὺ τῆς ψύξεως· τοσοῦτον γὰρ τὸ κακὸν δυσφύλακτον ὅσῳπερ καὶ τὴν ἡδονὴν ὑποδύεται τὸ βλάπτον. ἐκκλιτέον δὲ καὶ τὰς ὑπαίθρους κοίτας καὶ τὰς ἀπὸ τῶν ποταμῶν καὶ λιμνῶν ἀποπνεούσας αὔρας· οὐ γὰρ μόνον ψύχουσιν, ἀλλὰ καὶ ὑγραίνουσι τὰς ἕξεις. φυλακτέον δὲ καὶ τὰ πολύτροφα καὶ τὰ παχυντικὰ τῶν προσφερομένων, οἷον οἶνον νέον καὶ παχὺν καὶ στυπτικόν, ἄρτον σεμιδαλίτην ἄζυμον, φοίνικας, σταφίδας, ὠά, κοχλίας, βολβούς, ἰχθύων τοὺς πολυσάρκους, ταρίχων τοὺς τεμαχιστούς, κρεῶν τὰ ἄρνεια καὶ προβάτεια. οὐκ ἀμελητέον δ’ οὐδὲ τῶν γυμνασίων.

Athenaeus of Attalia in Oribasius, Medical Collections libri incerti 41, CMG VI 2,2 148,4-16 Raeder

“Autumn is less hot than summer, but less cold than winter. Thus, it is not simply hot or cold, since it is both, and neither of them in excess. But there is a different problem with it, one Hippocrates also mentioned in the Aphorisms, when he says: “whenever it varies between hot and cold on the same day, one must expect the illnesses of autumn” (Aphorisms III 4). And surely this is what makes autumn most likely to bring about illness: the variability of the mixture. So, it is not right to call it cold and dry, since it is not observed to be cold in itself, like winter, but compared with summer it is colder. And yet it is not evenly well mixed, like the spring, but it is different from that season in that it does not have a consistent good mixture and evenness through the whole day. For it is much hotter during midday than at dawn or dusk. Also, unlike spring, it is not precisely balanced between wet and dry, but it tends towards dryness. It has less dryness than summer, but not as much as it lacks heat. Clearly, then, as autumn is not to be called simply, as those others say, cold and dry. It has neither in extreme; sure, the dry does predominate over the wet, and one might rightly call it dry. But with respect to the difference between hot and cold, it is a mixture of both and it is variable.”

Ἀλλὰ καὶ τὸ φθινόπωρον ἧττον μὲν ἢ τὸ θέρος θερμόν, ἧττον δ' ἢ ὁ χειμὼν ψυχρόν. ὥστε ταύτῃ μὲν οὔτε θερμὸν ἁπλῶς οὔτε ψυχρόν, ἀμφότερα γάρ ἐστι, καὶ οὐδέτερον ἄκρως. ἕτερον δέ τι πρόσεστιν αὐτῷ κακόν, ὅπερ ἐπεσημήνατο καὶ Ἱπποκράτης ἐν Ἀφορισμοῖς εἰπών· ‘ὁκόταν τῆς αὐτῆς ἡμέρης ὁτὲ μὲν θάλπος, ὁτὲ δὲ ψῦχος ποιέῃ, φθινοπωρινὰ τὰ νοσήματα προσδέχεσθαι χρή’. καὶ τοῦτό γ'ἐστὶ τὸ μάλιστα νοσῶδες ἐργαζόμενον τὸ φθινόπωρον, ἡ ἀνωμαλία τῆς κράσεως. οὐκ ὀρθῶς οὖν εἴρηται ψυχρὸν καὶ ξηρόν, οὐ γάρ ἐστι ψυχρὸν αὐτὸ καθ' αὑτὸ θεωρούμενον, ὥσπερ ὁ χειμών, ἀλλὰ τῷ θέρει παραβαλ|λόμενον ἐκείνου ψυχρότερον. οὐ μὴν οὐδ' ὁμαλῶς εὔκρατον, ὡς τὸ ἔαρ, ἀλλ' ἐν τούτῳ δὴ καὶ μάλιστα διενήνοχεν ἐκείνης τῆς ὥρας, ὅτι τὴν εὐκρασίαν τε καὶ τὴν ὁμαλότητα διὰ παντὸς ἴσην οὐ κέκτηται. πολὺ γὰρ θερμότερόν ἐστι κατὰ τὴν μεσημβρίαν ἢ κατὰ τὴν ἕω τε καὶ τὴν ἑσπέραν. ὑγρότητος δὲ καὶ ξηρότητος οὐκ ἀκριβῶς μέν ἐστι μέσον, ὡς τὸ ἔαρ, ἀλλ' ἐπὶ τὸ ξηρότερον ῥέπει. λείπεται δὲ κἀν τούτῳ τοῦ θέρους, οὐ μὴν τοσοῦτόν γ' ὅσον θερμότητι. δῆλον οὖν, ὡς οὐδὲ τὸ φθινόπωρον ἁπλῶς οὕτω ῥητέον, ὡς ἐκεῖνοι λέγουσι, ψυχρόν τ' εἶναι καὶ ξηρόν. ἄκρως μὲν γὰρ οὐδέτερόν ἐστιν, ἐπικρατεῖ δ' ἐν αὐτῷ τὸ ξηρὸν τοῦ ὑγροῦ καὶ δικαίως ἂν λεχθείη ταύτῃ μὲν ξηρόν, ἐν δὲ τῇ κατὰ θερμότητα καὶ ψυχρότητα διαφορᾷ μικτὸν ἐξ ἀμφοῖν καὶ ἀνώμαλον.

Galen, De temperamentis i 4, I 527-528 Kühn