This is about the origin of the phrase ‘dog days’ because the origin informs us why we use the phrase. Dog days cover the hottest time of the year from July 3rd to August 11th. It originates in Roman times according to Dr Desmond Morris (Illustrated DOGWATCHING) when it was believed that Sirius, the Dogstar, added its heat to the sun’s leading to exceptional heat. The Romans called the time of year ‘dies caniculares‘ meaning the days of the dog.
Sirius is the brightest star in the night sky and its name is derived from the Greek word Σείριος, or Seirios, meaning ‘glowing’ or ‘scorching’. It is far too far from the Earth to really have any impact in terms of providing heat. It is 540,000 times further from Earth than the sun. However, it is about twice as hot as the sun at 10,000 degrees Celsius.
Some believed that the phrase referred to the time of year when dogs were driven mad due to excessive heat and rushed around in a frenzy. Only ‘mad dogs and Englishmen go out in the midday sun’ as the saying goes. This is another dog phrase referring to the stupidity of some Brits to go out in the sun, perhaps in hot places where they were unaware of the heat and its dangers to health.
