If you’re saying we’re in the “dog days” of summer right now because of how hot it is, you’re right… but your reasoning is actually wrong.
Because the “dog days” phrase actually isn’t a subjective term used to describe hot weather. It has an ancient astrological backstory (don’t we all, am I right?).
This particular backstory traces back to ancient Greece and Egypt, some 5000 years ago.
You see, the ancient Greeks and Egyptians noticed that the hottest parts of the summer happened during the 40 days in early summer when Sirius, the dog star, was visible in the constellation Canis Major, also known as “The Greater Dog”.
Sirius was the brightest star in the sky, but you could only see it from Egypt between July 3 and August 11.
Sirius also rises and sets with the sun for the summer, so ancient climatologists believed that the hot temperatures must be because the star was adding to the heat already being provided by the sun.
Hence, the “dog days” of summer: the time of year when temperatures are at their hottest thanks to an additional source of astrological heat.
A less interesting truth: Unfortunately, that isn’t actually what’s happening. Sirius is, in fact, more than 20 times brighter than the sun, so yes, it does give off a lot of heat, but it’s also 546,000 times further from Earth than the sun is.
That means the intensity of radiation from Sirius that actually reaches the Earth is miniscule compared to the energy received from the sun (and even miniscule might be an overstatement).
Consequently, the dog star has nothing to do with the hot temperatures typical of July and August. Still, it’s the reason why the “dog days” don’t necessarily align with the hottest days of the year.
Sara Tonks is a content meteorologist with weather.com and has a bachelor’s and a master’s degree from Georgia Tech in Earth and Atmospheric Sciences along with a master’s degree from Unity Environmental University in Marine Science.
