What does dog day afternoon mean?

Answer 1

The dog days were the days when the Dog Star, Sirius, rose just before sunrise. Ancient Romans believed that the hot days of late summer were caused by the Dog Star, and thought that dogs went mad during this time (also that wine spoiled, people became hysterical, and seas boiled!). Due to the precession, or movement of the universe, Sirius is no longer seen in the same position from Rome, but the expression has stuck. So a dog day afternoon would be the afternoon of one of the very hot, sticky days at the end of summer.

Answer 2

"Dog Day Afternoon" is a phrase that typically refers to a hot, oppressively uncomfortable day. It became popular as the title of a 1975 film starring Al Pacino, based on a true story about a bank robbery that took place on a scorching summer day in New York City.