The idea that extreme summer heat is linked to the stars may sound strange today, but for the ancient Greeks it was obvious. In fact, the belief that a mysterious star announced the arrival of the most stifling days endures in popular expressions. Even without knowing the scientific foundations in detail, they had already observed a connection between the celestial vault and the weather.
When temperatures rise until they become unbearable, we usually say it's a "dog day." Although it may seem that the phrase refers to animals, its history is much older and more surprising. The origin is in the sky and in a star that for Greeks and Romans had a very special meaning.
The brightest star and its link with Mediterranean beliefs
It was Sirius, which remains the brightest star that can be seen from Earth. Its rising at dawn coincided with the hottest days, and for those who lived in the Mediterranean basin, that coincidence was not accidental. Their constant observation of the sky led them to think that the brilliance of this star directly influenced the stifling heat.
The Greeks interpreted that the sun was not the only one responsible for the high temperatures, but that Sirius added its glow to it. That idea, full of symbolism, became part of their culture and their literature. The star's brightness was imagined to be so powerful that it could affect crops and people's health.
The heat of the gods under the lens of science
From that tradition came the word "canícula," which we use to refer to the most stifling days of summer. Its root is in the Latin term "canis," which means dog, and refers to the constellation Canis Major, where Sirius is located. Currently, the term is used to designate the period when the heat reaches its maximum intensity, generally in mid-July and August.
Current science has shown that the explanation of the ancients was more poetic than real. This interval of the year is among the hottest because Earth has accumulated weeks of solar radiation. In addition, Sirius's rising doesn't always occur on the same date, since it depends on the latitude from which it is observed.
How astronomical tradition keeps cultural memory alive
In cities like Athens, it occurs around mid-August, while in other regions of the Mediterranean it appears later. That lag shows that the relationship between Sirius and the heat could not be exact, although the tradition remained alive for centuries. What has endured is the power of words and the way they transmit cultural memory.
Today, no one believes that Sirius is to blame for heat waves, although its name and its myth are still present in our language. Saying it's a dog day is to unknowingly revive a belief that was born in Antiquity. Perhaps that is the true magic of the stars, which, in addition to illuminating, have taught us to put words to the most stifling summer.