The traditional “dog days” of summer fall between July 3 and August 11, noted for their extreme heat and humidity.
During this time of year, the star Sirius is at its brightest and can be seen rising alongside the sun. The phrase actually dates back to the Egyptians.
They believed that the star gave off extra heat and humidity to augment the already formidable heat of the sun.
Sirius is the “dog star” from the constellation Canis Major (Latin for “Big Dog”), hence the name.