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Meteorological background - Dog days: The hottest time of the year - Meteorology

Meteorological background – Dog days: The hottest time of the year – Meteorology


Meteorologists describe the period from July 23 to August 23 as Dog Days. But this term has nothing to do with four-legged friends. Its origin comes from the ancient Egyptians and is based on the star Sirius in the constellation of the Great Dog.

For the ancient Egyptians, the dog days began on the day the star Sirius appeared in the morning sky for the first time. Sirius is part of the constellation Canis Major. The end of the so-called dog days was marked on the day when the entire constellation could be recognized for the first time. It was exactly a month after Sirius made his debut.


dog days

The dogs are also very warm today.


Great Flood Warning

The dog days were of great economic importance to the ancient Egyptians, as the great Nile flood usually began with the appearance of Sirius. At this time, annual heavy rains began on the upper reaches of the Nile in Central Africa. However, in Egypt, no one could notice it, because it was dry all year round in Egypt, and the summer there lasted unchanged. Only Sirius indicated to farmers that they should seek higher areas to avoid the flooding of the Nile. But this was expected with great joy, because he brought the water necessary for Egypt.

The rotation of the Earth’s axis has changed history

For the ancient Egyptians, the dog days began in early July. However, since the Earth’s axis rotates in a circle every 26,000 years, the constellations can no longer be seen at the same time as they were in the days of the ancient Egyptians. The Romans didn’t see Sirius’ rise until late July, so the date on July 23, when the dog days began, probably goes back to Roman times. Today, Sirius can only be seen in the morning sky at the end of August. However, the history of dog days from Roman times has been preserved.

Heat comes from the Greeks

While Sirius was still a water indicator for the ancient Egyptians, it became a sign of warming for the Greeks. According to Greek myth, the fusion of sunlight with the blazing fire of the star Sirius is said to be the cause of the heat. Even today, the warmest days in the Mediterranean often occur during dog days and have come to be known generally as the weather rule, the so-called singularity. The term dog days is also incorrectly used today when a summer heat wave occurs outside this period.