Beating the Heat in the Dog Days of Summer

Discover how animals manage hot weather during the dog days of summer.

Cows Cooling Off in Water

A small herd of cattle cool off in a pond on a hot summer day.

Photo by Goce Risteski

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Last summer was a scorcher across much of the United States, with temperatures near or exceeding 100 degrees Fahrenheit for days and weeks on end. Here are some cool facts to help you cope with the lazy, hazy days of summer.

Ever wondered why the weeks from early July through early September are called the “Dog Days” of summer? The name comes from the ancient belief that when Sirius, also known as the Dog Star — the brightest star in Earth’s night sky — came in close proximity to the sun, it was responsible for extremely hot weather.

How hot is hot? Hot enough to fry the bill off a woodpecker? Or hot enough to fry an egg? The Everyday Mysteries website of the Library of Congress says it takes a skillet temperature of 158 F to fry an egg in the kitchen. But what about frying an egg in the direct sunlight? One informal study showed that a raw egg placed in a skillet with cooking oil can fry to a firm consistency in about 20 minutes in direct sunlight when the skillet temperature reached 135 F.

A couple summers ago, the folks at AccuWeather in State College, Pennsylvania, conducted an informal experiment to measure the surface temperature of several objects on a 100-degree day. They found that blacktop asphalt reached a temperature of 149, while a concrete sidewalk warmed up to 143, and the temperature of sand rose to 130 degrees. A light-colored car achieved a surface temperature of 136, while a dark-colored car reached 168.

What about the interior of your car on a hot day? Studies show that interior temperatures can exceed 125 F within just 20 minutes, climbing to 140 in less than an hour. That’s why it’s imperative that children and pets are not left inside a car during summer months, even for just a minute or two, and even if the windows are left cracked or rolled down.

The human body has between 2.5 and 3 million sweat glands, which help us cool down in extreme heat. Cows, on the other hand, mainly have sweat glands in their noses and around their shoulders, while dogs and cats have sweat glands in the pads of their feet. Pigs have no sweat glands, which is why they wallow in mud holes; the cool, muddy water protects their sensitive skin. Horses have the most sweat glands of any domestic animal — even more than a human. A horse subjected to an intense workout can lose as much as 10 to 15 quarts of sweat in an hour.

Chickens are prone to heat stress during periods of high heat and humidity, especially heavier and older birds. Broilers may stop gaining weight in hot weather, and layers may stop producing eggs. While chickens can’t sweat, the blood that flows through their combs and wattles helps them regulate their body temperature. Chickens also cool down in hot weather by panting, drinking more water, and taking dust baths.

Dogs, cats, sheep and cows also pant in hot weather. The saliva in their mouth wets the area, and as the drawn-in air flows across the animal’s tongue, it helps cool the body temperature. Since cows can’t turn up the air conditioning, and because they have few sweat glands to help them bear hot temperatures, you’ll often see cows standing knee- or chest-deep in pasture ponds and streams. Cows exposed to extreme heat eat less, and dairy cows produce less milk. That’s why many dairymen equip their dairies with misters, allowing the herd to stand under a cooling spray of water. Cattle without access to a mister or a pond will seek shade under trees or an open-sided loafing shed.

Experts say livestock can require twice as much water as usual in extreme heat. That means a 1,200-pound cow that normally consumes 10 or 15 gallons of water per day may need up to 30 gallons on an extremely hot day. A 200-pound pig that normally consumes 2.5 gallons of water daily may require 5 gallons, and a feeder lamb that typically drinks 1.5 gallons of water may very well drink as much as 3 gallons during extreme heat. And speaking of animal drinking habits, did you know that a camel can go weeks without water, but can drink up to 25 gallons of water at one time?

We humans also need to increase the amount of water we consume in extremely hot weather. A person who’s exercising or engaging in hard physical labor on a hot day can lose between 1 and 3 quarts of water to sweat. Experts recommend consuming 20 ounces of water before going outside, and drinking another cup of water every 15 minutes while working out in the heat. While a glass of iced tea or a cold beer may sound appealing during a heat wave, beer actually dehydrates your body, and drinks containing caffeine aren’t recommended.

Extreme temperatures are dangerous to livestock and humans alike. The Centers for Disease Control reports that about 6,000 people in the U.S. go to the emergency room each year with heat-related illnesses, and that extreme heat kills an average of 675 Americans annually.

However, no matter how hot it gets in your backyard, it could be worse. According to data from ClimateData.com, the world heat record was set in 1922 when temperatures in El Azizia, Libya, hit 136 F. Here at home, the all-time heat record was set in 1913 in Death Valley, California, when the thermometer read 134 F — and that’s just about hot enough to fry the bill off a woodpecker! 


Jerry Schleicher does his best to beat the smoldering heat of summer at his home in Parkville, Missouri.