You've heard of the dog days of summer, when long daylight hours and stifling temperatures make it hard to do much more than laze around like man's best friend — or maybe it's so hot that even dogs go mad.
But the so-called dog days aren't a reference to our four-legged companions at all. Rather, they are a reference to Sirius, the brightest star in the night sky.
Also called the “dog star” because of the way it trails nearby Orion, Sirius got the attention of the ancient Greeks and Romans, who noted that the star rose and set with the sun during summer months.
"People started thinking that the star gave off heat and added to the sun's warmth,” says Farmers’ Almanac managing editor Sandi Duncan, “and so they started being called the dog days of summer.”
We now know that the Earth's tilt toward the sun, not Sirius's star power, causes long, hot summer days in the northern hemisphere. Nevertheless, the term dog days (translated from the Latin dies caniculares) has stuck. According to the Farmers’ Almanac, they occur between July 3 and August 11 each year.
Long before the advent of air-conditioning, people coped with sweltering summer temperatures in clever ways. The Romans, for example, diverted water from aqueducts to run through pipes in their homes, which had a cooling effect. More recently, Duncan says, people used sleeping porches, splashed in open fire hydrants, or positioned fans to blow across blocks of ice.
This year's dog days have been marked by extreme heat, with weather agencies reporting record-breaking temperatures from Alaska to Europe. “The number of days with record highs has increased since the late 1970s,” says Rachel Licker, a senior climate scientist with the Union of Concerned Scientists, as has the frequency of heat waves, which have been on the rise since the mid-1960s.
The dog days are poised to get worse. In a recent report that used National Weather Service data, Licker and her colleagues found that the number of dangerously hot days is projected to increase dramatically, with the number of days with a heat index above 105 degrees expected to quadruple in the next few decades. That kind of extreme heat, their report cautions, poses a health risk for everyone, but especially older adults.
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As temperatures soar, experts say it's important to stay safe while savoring the waning days of summer. Here's how:
Understand the heat index
This is the “feels-like” temperature, Licker says, which takes into account both the air temperature and humidity level. The higher the humidity, the hotter it feels — and the difference can be dramatic: According to the National Weather Service, a 90-degree day with 50 percent humidity will feel like 95 degrees, while the same day with 75 percent humidity will feel like 105 degrees. Most smartphone weather apps and news reports will mention the feels-like temperature, along with any heat advisories. Pay attention to what they say before heading outside.
When it comes to staying cool, “fans don't cut it,” says Matthew J. Levy, an associate professor of emergency medicine at Johns Hopkins University School of Medicine. If you don't have access to air-conditioning at home, he recommends visiting a local library, mall or coffee shop during the day. Outdoor exercisers should avoid the early afternoon, when temperatures are highest, or shift their workouts indoors, according to the American Heart Association.
Quench thirst wisely
Despite the popular recommendation of eight 8-ounce glasses of water a day, experts say the amount you really need depends on factors like weight and activity level. By the time you're thirsty, Levy says, you're already dehydrated — a sign to up your fluid intake. As for alcohol? Use moderation. It not only causes dehydration, there's also evidence that it may also increase sunburn risk.
Know your personal risk
It becomes harder for our bodies to regulate their temperature as we get older, Levy says, and certain prescription medications (like those for high blood pressure) and chronic conditions like respiratory diseases can add to the challenge. The bottom line? Don't be shy about bringing specific health concerns to your primary care physician, Levy says. They can advise you about your risk factors and ways to cope.
Be sun- and sunscreen-smart
Between sticks, sprays, creams and powders, the number of sunscreens on the market can be overwhelming. Fortunately, the American Academy of Dermatology's recommendations are straightforward: Look for a label that specifies SPF of 30 or above, broad-spectrum protection, and a water-resistant formula. The organization also recommends wearing sunglasses and a wide-brimmed hat, and seeking shade between 10 a.m. and 2 p.m., when the sun's rays are the strongest. When it comes to clothing, long sleeves and pants can also offer sun protection. To keep cool, Levy recommends opting for loose-fitting clothing and moisture-wicking fabrics.
Outdoor parties, picnics and barbecues are fun for all — but can quickly become a breeding ground for the harmful bacteria that cause food poisoning. Do not leave perishable foods unrefrigerated for more than two hours at room temperature (one hour if the temperature is 90 degrees or hotter), says the Centers for Disease Control and Prevention (CDC). If you're in charge of the grill, clean it off before you start and use fresh utensils and a new plate to remove meat when it's done cooking.
Beat the bugs
With outdoor activities like hiking and camping in full swing, so is the risk of bites from pests like ticks and mosquitos. The CDC recommends using an insect repellent with active ingredients like DEET, Picaridin, or oil of lemon eucalyptus. Long sleeves and pants can help ward off mosquitoes, but battling ticks means taking additional measures, like treating clothing and gear with the chemical permethrin and checking your body, pets and possessions for any hangers-on once you come indoors.
Protect your pets
Just like us, dogs and cats need special care when temperatures soar. The American Society for the Prevention of Cruelty to Animals offers some pointers: Pets should have access to plenty of clean, fresh water and an air-conditioned place to rest. Never leave an animal in a hot car, and limit walks on hot pavement, which can quickly burn paws.