It is a common misconception that the term came from the heat being not fit for a dog. It comes from the constellation Canis Major, The Greater Dog. Sirius is a part of the constellation and is the brightest visible star from any part of the Earth. The Ancient Romans. believed that since the Sun and Sirius rose and set in conjunction, that the star was giving off additional heat

This period is usually the hottest part of summer for those in the Northern Hemisphere not due to Sirius but, The Earth's tilt allowing