Dog days Dog days The dog days or are the hot, sultry days of summer. They were historically the period following the heliacal rising of the star system Sirius, which Greek and Roman astrology connected with heat, drought, sudden thunderstorms, lethargy, fever, mad dogs, and bad luck. They are now taken to be the hottest, most uncomfortable part of summer in the Northern Hemisphere. The English name is a calque of the Latin "" (."the puppy days"), itself a calque of the Greek "kynádes hēmérai" (, "dog days"). The Greeks knew the star α Canis Majoris by several names, including Sirius (,
Dog days "Seírios", "Scorcher"), Sothis (, "Sôthis", a transcription of Egyptian "Spdt"), and the Dog Star (, "Kúōn"). The last name reflects the way Sirius follows the constellation Orion into the night sky. Sirius is by far the brightest proper star in the night sky, which caused ancient astronomers to take note of it around the world. In Egypt, its return to the night sky became known as a precursor to the annual flooding of the Nile and was worshipped as the goddess Sopdet. In Greece, it became known as the precursor of the unpleasantly hot phase of the summer. Greek poets