Published: July 20,2017
The "dog days" of summer are in full swing as portions of the nation bake in 90- and 100-degree heat during what is climatologically the hottest time of the year.
We use this saying every year around this time, and its origins date back thousands of years.
The phrase dog days goes all the way back to the ancient Egyptians, who reigned from around 3100 B.C. to 332 B.C. in northeast Africa.
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The ancient Egyptians believed exceptionally hot weather was directly related to the appearance of the dog star Sirius in the constellation Canis Major.
Sirius is visible in Egypt's sky from about July 3 to August 11. Therefore, the dog days are technically over by mid-August despite the modern interpretation which typically portrays endless heat that may define the month of August.
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Sirius, in the constellation Canis Major, is the closest star visible with the naked eye from the Northern Hemisphere's mid-latitudes.Ancient Egyptians thought the energy from Sirius combined with the sun's energy to produce heat waves.
Sirius is approximately 23 times brighter than the sun, but the dog star is 546,000 times farther from the Earth. As a result, the intensity of the radiation that reaches the Earth from Sirius is minuscule in comparison to the energy received from the sun.
Consequently, the dog star has nothing to do with the hot temperatures typical of July and August other than an ancient saying that we continue to use each summer to describe the uncomfortable conditions.
Brian Donegan is a digital meteorologist at weather.com. Follow him on Facebook and Twitter.
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