Hottest days of the year in Northern Hemisphere. Usually about 40 days, but variously reckoned at 30- 54 days. Popularly believed to be an evil time when the sea boiled, wine turned sour, dogs grew mad, and all creatures became languid, causing to man burning fevers, hysterics and phrensies (from Bradys Clavis Calendarium, 1813).
Originally the days when Sirius, the Dog Star, rose just before or at about the same time as sunrise (no longer true owing to precession of the equinoxes). Ancients sacrificed a brown dog at the beginning of Dog Days to appease the rage of Sirius, believing that star was the cause of the hot, sultry weather.
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