The Dog Days of Summer
The “dog days of summer” occur during the hottest and muggiest
part of the season. Webster defines “dog days” as
The period between early July and early September when the hot sultry weather of
summer usually occurs in the northern hemisphere.
Why do we call the hot, sultry days of summer
The Term dog days has an interesting origin.
In ancient times, when the night sky was unobscured by artificial lights and
smog different groups of peoples in different parts of the world drew images in the sky by
“connecting the dots” of stars. The images drawn were dependent upon the
The Chinese saw different images than the Native Americans, who saw different pictures than
the Europeans. These star pictures are now called constellations, and the constellations
that are now mapped out in the sky come from our European ancestors.
They saw images of bears, (Ursa Major and Ursa Minor), twins, (Gemini), a bull,
(Taurus), and others, including dogs, (Canis Major and Canis Minor).
The brightest of the stars in Canis Major (the big dog) is Sirius, which also happens to be
the brightest star in the night sky. In fact, it is so bright that the ancient Romans thought
that the earth received heat from it. Look for it in the southern sky (viewed from northern latitudes) during January.
In the summer, however, Sirius, the “dog star,” rises and sets with the sun. During
late July Sirius is in conjunction with the sun, and the ancients believed that its heat added to the heat of the sun, creating a stretch
of hot and sultry weather. They named this period of time, from 20 days before the
conjunction to 20 days after, “dog days” after the dog star.
The conjunction of Sirius with the sun varies somewhat with latitude. And the
“precession of the equinoxes” (a gradual drifting of the constellations over time) means
that the constellations today are not in exactly the same place in the sky as they were in ancient Rome. Today, dog days occur during the period between July 3 and August 11. Although it is certainly the warmest period of the summer, the heat is not due to the added radiation from a far-away star, regardless of its brightness. No, the heat of summer is a direct result of the earth’s tilt.