What are the “dog days of summer”?

In late August and early September, look for a hint of the changing season in the predawn sky: Orion the Hunter and Sirius the Dog Star. The very noticeable constellation Orion the Hunter rises before dawn at this time of year, recognizable for the short straight line of three stars that make up Orion’s Belt. And the sky’s brightest star Sirius – sometimes called the Dog Star because it’s part of the constellation Canis Major the Greater Dog – follows Orion into the sky as the predawn darkness gives way to dawn. (Image credit: EarthSky.org)

The term “dog days of summer” refers to a time of hot and humid weather in the Northern Hemisphere, usually in July and early August.

The phrase is not a reference to lazy dogs lying around on hot and humid days. It refers to the stars in the sky.

This time period coincides with the rising of the star of Sirius, or the Dog Star. Sirius is part of the “Greater Dog” constellation Canis Majoris. Sirius follows Orion, as a faithful dog would.

Sirius is by far the brightest proper star in the night sky, which caused ancient astronomers to take note of it around the world. In ancient Greece and Rome, the dog days were believed to be a time of drought, bad luck and unrest.

The Old Farmer’s Almanac considers the dog days to be the 40 days beginning July 3 and ending August 11. Over time, constellations drift with reference to Earth. For the ancient Romans, the dog days of summer occurred from about July 24 to around August 24.

There is no formal meteorological or climatological definition.

A traditional verse forecasts bad outcomes when this time of year is associated with rainfall, and a good year when it is sunny:

Dog Days bright and clear

Indicate a happy year;

But when accompanied by rain,

For better times, our hopes are vain.

Category: Meteorology, Seasons

Comments Off on What are the “dog days of summer”?

Comments are closed.