The dog days, around when Sirius rises, really the hottest days of the year
July and August are generally known as the hottest months of the year in the Northern Hemisphere, the hottest period can vary from year to year. And depending on your latitude, the astronomical dog days can come at different times.
In Athens, for instance, Sirius will rise around the middle of August this year. But farther south, it’ll happen earlier in the year; farther north, it’ll happen later.
There’s another reason that the dog days don’t correspond neatly with the heat: the stars in Earth’s night sky shift independently of our calendar seasons.
“Our Earth is like a spinning top“If you toss it onto a table, after it slows down … the pointing direction of the top will slowly go around in circles.” Similarly to a top, “the Earth’s rotation is kind of wobbling around.”
“The calendar is fixed according to certain events, but the stars have shifted according to the way that the Earth wobbles,” “So in about 50-some years, the sky shifts about one degree.”
This means that the dog days of ancient Greece aren’t the dog days of today. What it also means is that several millennia from now, this astrological event won’t even occur during the summer.
“In 26,000 years, the dog days would completely move all around the sky,” said Schaefer. “Roughly 13,000 years from now, Sirius will be rising with the sun in mid-winter.”
Ah yes, the dog days of winter. When it’s so cold that even the dogs lie around the fire, trying to stay warm.
The “dog days,” I always thought, were those summer days so devastatingly hot that even dogs would lie around on the asphalt, panting.
Many people today use the phrase to mean something like that—but originally, the phrase actually had nothing to do with dogs, or even with the lazy days of summer. Instead, it turns out, the dog days refer to the dog star, Sirius, and its position in the heavens.