Dog days facts for kids

The dog days are the hottest and often most uncomfortable part of summer.

The English name "dog days" comes from the Latin phrase dies caniculares, which means "puppy days." This Latin phrase was a translation of the ancient Greek kynádes hēmérai. The Greeks called the bright star Sirius the "Dog Star" because it seemed to follow the constellation Orion across the night sky. Ancient people believed Sirius brought heat, drought, sudden thunderstorms, and even bad luck.

In some countries, like Sweden (rötmånaden) and Finland (mätäkuu), the name means "rot month." This is because in the hot summer, food used to spoil quickly. Also, wounds might heal slower or get infected more easily during these warm months.

A Look Back: The History of Dog Days Beliefs

Sirius, the Dog Star, can be found by following the line of Orion's Belt in the night sky.

Sirius is the brightest star we can see in the night sky. Because of its brightness, ancient astronomers all over the world noticed it.

In ancient Egypt, when Sirius reappeared in the sky, it signaled the start of the annual flooding of the Nile River. Egyptians even worshipped it as the goddess Sopdet.

In ancient Greece, people believed Sirius's return brought the very hot and unpleasant part of summer. Greek poets wrote that the bright star caused heat and fevers. It was also linked to sudden thunderstorms. For example, the poet Homer described how the star Sirius was seen as a sign of trouble, bringing heat and fevers to people.

Another Greek poet, Hesiod, thought the hottest part of summer was just before Sirius reappeared. He believed Sirius was still in the sky, even if invisible, making the sun's power even stronger. People thought this combination of Sirius and the sun affected plants, animals, and people. They believed it made the land dry and caused people to feel tired.

Vegetation on Crete dried out by the August heat.

The Romans also connected Sirius to the summer heat, tiredness, and illnesses. The writer Pliny even noted that dog attacks seemed to increase in July and August. He suggested feeding dogs chicken manure to calm them down!

Historically, people in western medicine also had beliefs about the dog days. For instance, a 1564 English book advised against certain medical treatments during this time. A 1729 British book claimed that the sun's heat was so strong that people would sweat at midnight. It also warned that injuries could become more serious.

An old drawing from the 9th century showing the constellation "Canis Major", which includes Sirius.

Even after people stopped believing in astrology as much, the "dog days" continued to mean the hottest part of summer. Farmers in North America had a saying:

This meant they preferred dry weather during the dog days for a good harvest.

Children cooling off in a public fountain in New York during the dog days of 1904.

When Are the Dog Days? Dates and Changes

The exact dates for the dog days have changed over time and in different places. Historically, they often started around mid-July and lasted for about 30 to 60 days.

In Anglo-Saxon England, the dog days could run from mid-July to early or mid-September. In the 16th century, the Church of England observed them from July 7 to September 5. Later, these dates were shortened to July 19 to August 20. When Great Britain adopted the modern Gregorian calendar in 1752, the dates shifted again, from July 30 to September 7.

Today, many English-speaking countries consider the dog days to be from July 3 to August 11. This period usually includes the hottest part of summer.

The Science Behind Summer's Hottest Days

Orion (right) and Sirius (bottom), as seen from the Hubble Space Telescope.

Even though Sirius is the brightest star in our night sky, it is very far away from Earth. It is about 8.7 light-years away! This means Sirius has absolutely no effect on our planet's weather or temperature.

The star Sirius does appear in the night sky in late summer, but its position slowly changes over thousands of years. In about 10,000 years, it will rise in the middle of winter instead of summer.

The real reasons for summer heat and rainfall patterns are much closer to home. They depend on many factors like your location's latitude, how close it is to the sea, and ocean currents like the Gulf Stream. For example, London, UK, is further north than Calgary, Canada, but has milder weather because of the sea and the warm Gulf Stream.

Some medical studies have looked into whether the dog days in Finland are linked to a higher risk of infection after surgery. However, this research is still being checked and confirmed.

See also

• Heat wave
• Indian summer
• Silly season
• Star lore