“It’s not just the heat. It’s the humidity.” That statement is almost a mantra during summer months, and you may find yourself rolling your eyes when you hear it for the hundredth time during spin class.
However, there’s actually a lot of truth to it! Humidity doesn’t just leave you longing for a wet wipe — it can make it much harder to cool down on a hot day. Here’s how it all works, plus some tips to beat the heat.
How Your Body Cools You Down
On a hot day, your body relies on the surrounding air to help you cool down. You start sweating when you get hot. As dry air passes over your skin, your sweat evaporates, taking some of your body heat with it. By drawing heat away from your body, air and sweat work together to cool you off. This process is called evaporative cooling.
Humid air is full of water particles. In fact, at 60% relative humidity, there are 92 grains of water per pound of air. For context, it takes 7,000 grains of water to make one pound.
Evaporative cooling doesn’t work as well on a humid day because water doesn’t evaporate easily in high humidity. Your sweat will simply stick to your skin. Consequently, your body heat won’t evaporate and you’ll have a harder time keeping cool.
How Does Humidity Dehydrate You?
It might seem backward, but it’s actually possible to get dehydrated faster during wet conditions than dry. How can that be?
In a humid environment, as you start to sweat and still feel hot, your body may try even harder to lower your body temperature. You might sweat more profusely than normal. This process dehydrates you faster.
If you’re sweating a lot, you have to drink a lot more water than normal to stay hydrated on a humid day. You’ll also need a greater amount of electrolytes — salt dissolved in water, often mixed with sugar to help you absorb it better — to replenish those you lose by sweating.
Hot Tips For Chilling Out
Evaporative cooling works extremely well in the desert because the air is so dry. Kangaroos in the Australian Outback, for example, lick their arms so the dry air will evaporatively cool them. Luckily, you have more dignified ways to beat the heat! Try these suggestions.
Start by taking short trips outside and letting yourself get used to the heat and humidity, gradually increasing the amount of time you spend outside each day. Eventually, you should start to sweat earlier and more heavily than you used to. Be sure to stay hydrated throughout this process.
Drink Electrolyte Drinks
Along with water, it’s important to replenish any salt and sugar your body loses in the heat. Store-bought sports drinks often contain copious amounts of sugar. Plus, they come in disposable plastic bottles and can get expensive quickly. You can make your own electrolyte drinks to save money, help the environment and create your favorite flavors.
Avoid the Hottest Part of the Day
Try to limit your outdoor excursions to dawn and dusk during very hot, humid weather. A nighttime stroll under the stars is downright magical in the summer!
Wear a Cooling Vest
Need to work outdoors in the heat? A cooling vest very well might save your life. Although high-end cooling vests can be — ahem — an investment, they keep your body cool by means of a refrigerant that circulates around your torso. Less expensive cooling vests use a series of ice packs to cool you down, but they can still be very effective.
Keeping Your Cool
You’re not imagining it — hot, humid air really does make it harder to regulate your body temperature by throwing your evaporative cooling system out of whack. Thankfully, there are many other ways to stay cool, even on the muggiest of days. Learn the signs of dehydration and heat-related illness to stay safe in hot weather. And, as always, keep your water bottle close by.
Jane is an environmental writer and the founder and editor-in-chief of Environment.co where she covers sustainability and eco-friendly living.