Why are these hot, humid days of August called Dog Days?

Question

Why are these hot, humid days of August called Dog Days?

Answer 1

If I hadn't just heard about the constellation side of things, I would have assumed that it had to do with the fact that it is so hot and humid that you just want to lay around like the dogs do!!  I know that's how I feel here in Houston!

Answer 2

They're named for the star Sirius, in the constellation Canis Major.  see http://wilstar.com/dogdays.htm

Answer 3

The term "Dog Days" was used by the Greeks (see, e.g., Aristotle's Physics, 199a2), as well as the ancient Romans (who called these days caniculares dies (days of the dogs)) after Sirius (the "Dog Star"), the brightest star in the heavens besides the Sun.

Popularly believed to be an evil time "when the seas boiled, wine turned sour, dogs grew mad, and all creatures became languid, causing to man burning fevers, hysterics, and phrensies" - Brady’s Clavis Calendarium, 1813.[citation needed][page # needed]

The Dog Days originally were the days when Sirius, the Dog Star, rose just before or at the same time as sunrise (heliacal rising), which is no longer true owing to precession of the equinoxes. The ancients 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.