July 3 is the beginning of the Dog Days of Summer. The “dog days” are the particularly hot and humid days that take place during the year. These days traditionally run for 40 days, from July 3 to August 11. These days historically align with the rising of the star Sirius, known as the “Dog Star”, with the sun.
The History Behind the Hottest Days of the Year
During this time of the year in ancient civilizations, when the brightest star—Sirius—rose with the sun, people saw this as a warning. During this time, with the added heat, ancient people experienced drought, illness and social unrest. Because of this, they associated this time with danger.
The term “Dog Days” comes from the name of the star “Sirius”, which is the brightest star in the constellation Canis Major, known as the “Greater Dog”. The timing of this star appearing in the night sky marked a dangerous time for ancient people. Therefore, when ancient civilizations saw Sirius rising with the sun, marking the start of the Dog Days of Summer, this also marked a time of hardship.
Constellations appear and disappear throughout the year. They can be used to mark the seasonal changes. Try it yourself with our various free worksheets on constellations and tracking:
Constellations Map
Planet Tracking
Seasons Tracker
The Science Behind the Hottest Days of the Year
The hottest days of the year occur for most of July and nearly half of August. Yet, the longest day of the year happens in June. Why do the hottest days come weeks later? The longest day of the year is the summer solstice. This is the day when the sun is out and shinning for the longest amount of time all year. One would think that the longer the sun is shinning, the hotter it should be. But rarely is the summer solstice also the hottest day of the year.
The reason for this has to do with how the earth absorbs, stores and releases energy from the sun. Imagine bringing a pot of water to a boil on the stove. When the burner (the sun) reaches its highest temperature setting, the water (the earth) continues to warm up and some time goes by before it actually comes to a boil.
After the summer solstice, the earth continues to get more solar energy than it loses each day. Therefore, the temperature keeps rising. Eventually, this balances off and temperatures start to level before going down. This is the time when the hottest days of the year are experienced. Conduct your own experiment to see how the sun warms the earth with this free worksheet:
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