"Dog Days" of Summer Begin Today, July 3, Through August 11

The “Dog Days” of Summer officially start today, Wednesday, July 3. Most people casually refer to the "Dog Days" as a period of hot and humid weather. But did you know that the dog days are a 40-day period which lasts from early July through mid-August?

The dog days of Summer run from July 3 through August 11 in the Northern Hemisphere and have to do with the star Sirius, known as “the dog star.” Sirius is the brightest star in the Northern Hemisphere other than the Sun, and it is found in the constellation Canis Major; thus the name “dog star.”

In the Summer, Sirius rises and sets with the Sun. During late July, Sirius is in “conjunction” with the Sun. 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, the “dog days” after the dog star.

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 culture.

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. The star can be seen prominently in the Winter in the Northern Hemisphere, adjacent to Orion the Hunter.

The conjunction of Sirius with the Sun varies somewhat with latitude. Also, the constellations today are not in exactly the same place in the sky as they were in ancient Rome. Although we are in the middle of the dog days of Summer right now, the heat is not due to the added radiation from a far-away star, regardless of its brightness. The heat of Summer is a direct result of the earth’s 23.5 degree tilt on its axis, meaning the Northern Hemisphere is tilted toward the Sun during the Summer.

Welcome to the "Dog Days."

Paul