Why Do We Call Them “Dog-Days”?
When we talk about “dog-days” now, we mean the period of the year between July 3d and August 11th, twenty days before and after the rising of the “dog-star.”
The name was applied by the ancients to a period of about forty days, the hottest season of the year, at the time of the rising of Sirius, the dog-star.
The time of the rising is now, owing to the precession of the equinoxes, different from what it was then (July 1st). It is now about July 23d.