The dog days of summer: What they mean for Texas

We’re in the dog days of summer, and we’ll be in them for a while. But what are they exactly and what does it mean in Texas? Here are five things to know about the dog days of summer:

1. ‘Dog days’ isn’t just a phrase, they have real dates

Although the dog days of summer traditionally has referred to the hottest days of the year, the days are actually a specific period: July 3 to Aug. 11 every year. The phrase, though, can be traced back thousands of years to the days of the Roman Empire, according to the National Weather Service.

In some major Texas cities, the dog days of summer and the climatologically hottest days of the year do overlap when you look at the benchmark “normal” temperatures the weather service uses. Those temps are based on 30 years of climate data from 1991 to 2020.

• The hottest time of the year in Houston, on average, is between July 29 and Aug. 12, when temperatures normally reach an annual peak of 96 degrees. If the occurrence of 100-degree days is your preferred metric for hottest period, then Houston has recorded triple-digit temperatures, on average, from July 19 to Aug. 17.
• In San Antonio, the hottest time of the year, or when the normal annual maximum temperature of 97 degrees is reached, would be between July 30 and Aug. 16. But San Antonio has recorded triple-digit temperatures, on average, from June 26 to Aug. 26.
• Austin’s average annual peak temperature is 99 degrees from July 31 to Aug. 14. However, the Texas capital has recorded triple-digit temperatures, on average, from July 4 to Aug. 30.

2. Dog days refer to a stellar ‘dog’

The dog days of summer, July 3 to Aug.11, begin 20 days before and 20 days after Sirius, the brightest star in the constellation Canis Major (“larger dog” in Latin), rises and falls in conjunction with our sun, according to the weather service.

“Constellations change as the days and months go by, so most people don’t see the full Canis Major until the wintertime,” Saul Rivera, public program specialist for the University of Texas McDonald Observatory, told the San Antonio Express-News last year. “During the summer, it’s rising along with the sun, and you can see them side by side.”

3. Sirius has an ancient history

Sirius originates from the ancient Greek word “seirios,” which means “scorching” or “glowing.” In ancient Greece, Egypt and Rome, it was believed that Sirius’ dawn rising in summer led to extreme weather, such as heat, drought, thunderstorms and river flooding, Rivera said. Ancient people described these days as times when both humans and dogs would go mad from the heat.

Rivera said later observers would see Sirius rising brightly in the sky, followed by the sun, and believed that both were contributing to the scorching temperatures on Earth. They referred to this as “double star heat.”

That idea fell by the wayside once it was known that heat from Sirius would have to travel 8.6 light years (or about 50.6 trillion miles), while the sun is, on average, only 93 million miles away.

4. Sirius has been seen as an omen

Ancient Egyptians welcomed the appearance of Sirius, which often coincided with Nile River floods that brought rich soil needed to grow crops in the desert climate, according to The Old Farmer’s Almanac. While no one in Egypt knew exactly when the flooding would start, they did notice that the water rose on days when Sirius (known to them as Sothis) also before the sun. They used the star as a “watchdog” to forecast the event.

On the other hand, ancient Greeks and Romans linked Sirius to periods of prolonged heat and dryness that were believed to cause lethargy, fevers, increased illness and overall misfortune.

5. Dog days are a good reminder of pet heat safety

Speaking of dogs and summer, remember to practice heat safety with your pets, especially in the dangerously hot and humid Texas summers. The weather service recommends that pet owners in summer:

• Have an emergency evacuation plan for pets to avoid leaving them behind during tropical storms, hurricanes or flooding.
• Pets are especially susceptible to heat illness, so try to keep your animals hydrated.
• Never leave pets inside a vehicle, where interior temperatures can rapidly turn deadly.