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 (,
Sirius The other two are the Hyades and the Pleiades, and each of these clusters consists of hundreds of stars. In 2017, a massive star cluster was discovered only 10' from Sirius. It was discovered during a statistical analysis of Gaia data. The cluster is over a thousand times further away from us than the star system. The most commonly used proper name of this star comes from the Latin "Sīrius", from the Ancient Greek "Σείριος" ("Seirios", "glowing" or "scorcher"), although the Greek word itself may have been imported from elsewhere before the Archaic period, one authority suggesting a link with