So I looked it up.
The ‘dog days of summer’ is an expression used to describe the uncomfortably hot, sultry days of summer. There’s a lot to do about Greek and Roman astrology, but the short of it is that it is connected to the star Sirius, in the constellation Canis Major (Greater Dog). It is known more commonly as the “dog star”.
Because it’s the brightest star in the sky, it received a lot of attention from ancient astronomers. It became known as the precursor to the unbearably hot phase of summer. People believed that this star was responsible for bringing the hottest and driest periods of the summer.
Ready for some science?
While it is true that Sirius is the brightest star in the sky from Earth, it has no effect on the planet’s weather or temperature. Also true is that the star continues to return to the night sky in the Northern hemisphere in late summer. However, its position will continue to shift gradually and in about 10,000 years, it will actually appear in the middle of winter.