George Stubbs (English artist, 1724-1806) White Poodle in a Punt 1780
Dog Days of Summer is the name for the most sultry period of summer, from about July 3 to Aug. 11. Named in early times by observers in countries bordering the Mediterranean, the period was determined to extend from 20 days before to 20 days after the conjunction of Sirius (the dog star) & the sun. The Greek poets Hesiod (ca. 750-650 BCE) & Aratus (ca. 310–240 BCE) refer, in their writings, to "the heat of late summer that the Greeks believed was actually brought on by the appearance of Sirius," a star in the constellation, that the later Romans, & we today refer to as Canis Major, literally the "greater dog" constellation. Homer, in the Iliad, references the association of "Orion's dog" (Sirius) with oncoming heat, fevers, & evil, in describing the approach of Achilles toward Troy:
Sirius rises late in the dark, liquid sky
On summer nights, star of stars,
Orion's Dog they call it, brightest
Of all, but an evil portent, bringing heat
And fevers to suffering humanity.