“Dog Days” (Latin: dies caniculares) are the hottest, most sultry days of summer. In the Northern Hemisphere, the dog days of summer are most commonly experienced in the months of July and August, which typically observe the warmest summer temperatures. The name comes from the ancient belief that Sirius, also called the Dog Star, in close proximity to the sun was responsible for the hot weather.
The Romans referred to the dog days as “dies caniculurus” and associated the hot weather with the star Sirius. They considered Sirius to be the “Dog Star” because it is the brightest star in the constellation Canis Major (Large Dog). Sirius is also the brightest star in the night sky.
The Dog Days originally were the days when Sirius rose just before or at the same time as sunrise (heliacal rising), which is no longer true, owing to precession of the equinoxes.Here i had to look that up and found ” Earth goes through one such complete precessional cycle in a period of approximately 26,000 years.”
The Romans sacrificed a brown dog at the beginning of the Dog Days to appease the rage of Sirius, believing that the star was the cause of the hot, sultry weather.
Dog Days were popularly believed to be an evil time “the Sea boiled, the Wine turned sour, Dogs grew mad, and all other creatures became languid; causing to man, among other diseases, burning fevers, hysterics, and phrensies.”