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Dear Tom,
I just heard a reference on a radio program about the “dog days” of summer. What does that mean?
—Sharon W. Naperville
Dear Sharon,
The term “dog days” refers to the periods of hot and humid weather that typically occur in parts of the Northern Hemisphere in July and August. During late summer, Sirius, also known as the Dog Star because of its location in the constellation Canus Major (Great Dog), is not visible in the sky because it rises and sets with the sun. Ancient people thought that the hot, sultry weather conditions were caused by Sirius, the brightest star in the sky, was adding its heat to the sun’s. Astronomically, the Egyptians calculated the “dog days” from July 3 to Aug. 11. In Mediterranean areas, that time was also plagued by disease and discomfort, and the added heat was thought to be the cause of seasonal flooding on the Nile.