- The hot, sultry period of summer between early July and early September.
- A period of stagnation.
Origin of dog daysTranslation of Late Latin diēs canīculārēs, Dog Star days (so called because the Dog Star (Sirius) rises and sets with the sun during this time) : Latin diēs, pl. of diēs, day + Late Latin canīculārēs, pl. of canīculāris, of the Dog Star.
(normally plural, singular dog day)
- "Dog days" have long carried an association as the hottest, most stagnant, and unwholesome time of the year, usually July 3 to August 11, but variously calculated, depending on factors such as latitude, historical period, or whether the lesser star Procyon is also reckoned. Specifically, the heliacal rising of Sirius has shifted down the calendar with the precession of the equinoxes, making the exact dates of the "dog days" significantly distinct now from those in former times.
Attested in English since 1538, from Latin dies caniculares, translated from Ancient Greek; originally a reference to the hot summer days (in the Northern Hemisphere) when Sirius (the Dog Star), in Canis Major, rose and set with the Sun (heliacal rising). The Greeks also made reference to these "dog days", and for the ancient Egyptians, circa 3000 BCE, the rising of this star coincided with the summer solstice and the start of Nile flooding. The "dog" association apparently began here, as the star's hieroglyph was a dog, a watchdog for the flooding of the Nile.