As a child I believed that the so-called Dog Days of summer were called that because the intense heat causes dogs to pant more than usual to keep their body temperature down. And while my observation was not entirely misguided, I found out later that the appellation comes from the approximately six-week period when the rising of the sky's brightest star, Sirius—the so-called Dog Star associated with the constellation Canis Major, the "greater dog"—occurs before the Sun, making it visible to observers in the Northern Hemisphere.
The modern starting date is usually said to be July 3, and the ending date is August 11—though most people think of the Dog Days as extending into late August or even early September since they associate this period with exceptionally hot, humid weather in the Northern Hemisphere.
It was in preparation for such days that during my first summer in the District of Columbia, my landlady instructed her handyman to install an air conditioner in the window of the room I rent in a cavernous home in northwest Washington. She insisted that I would never make it through a hot, humid D.C. summer without air conditioning. I told her that I was pretty heatproof and that I would make it just fine. After all, I grew up in Michigan and managed the hot, humid summers there without air conditioning.