While it’s common knowledge that staying hydrated in warm weather is important, we talk less about how it’s just as vital to stay on top of your water intake in the winter. With cooler temperatures comes less sweating, and thus less thirst — so hydration might not be a top priority. No matter what time of year it is, staying hydrated is a must. And in winter months, especially, there are many reasons why getting enough fluid intake is a legitimate concern.

Whether you're a serious endurance athlete, a winter sports enthusiast, or a little bit of both, we've gathered the top reasons from sports scientists and pro triathletes on why it’s important to stay hydrated and healthy when training during the winter months, plus some tips on how to do that. (Of course, we recommend consulting a licensed dietitian or healthcare practitioner before making any decisions about nutrition).

Why Does Hydration Matter?

Colder Means Drier

Cold weather doesn’t mean just dry air — our bodies also “dry out” as we lose more water in chillier surroundings. As army dietitian and triathlete Trisha Brooke Stavinoha points out, "We can lose as much fluid training in the cold as we do in the heat, but in different ways." In mild temperatures, athletes generally lose about 600 to 2000 ml per day through breathing. But when exercising in cold climates, which is any temperature of 30°F or below, the combination of dry air and high altitude causes the body to lose even more fluids. Breathing cold air also dries the respiratory tract, which is why it is important to moisten the air with enough fluid intake.

Also, keep in mind that you will lose an additional 500 mL of fluid through urination. As Stavinoha explains, "The body responds to cold by tightening the blood vessels to conserve heat, which results in increased urination or cold-induced diuresis (CID)." Another source of fluid loss is through sweating. With all the extra layers of clothing, it might take longer to sweat in the cold, but athletes will still sweat when training. In fact, endurance athletes training in cold weather will lose between 1/2 to 1 liter per hour.

Athletes Sweat More But Thirst Less

Complicating matters even more, cold can alter the body's thirst sensation, which is why it is important to get enough fluids throughout your workout. Athletes may also not feel cold until they stop moving and are soaking wet with sweat. These two factors can significantly increase the chances of hypothermia, a dangerous condition that leads to drowsiness, disorientation, extreme fatigue, and even death. Once it sets in, drinking fluids will not be enough to raise your core body temperature from 95°F (the danger zone) to 98.6°F, which is normal. This is why it is vital to not get dehydrated and also change into warm, dry clothes immediately after exercising. If you’re going to be outside for most of the day, make sure to pack a change of clothes in your gear bag.

How to Stay Hydrated

A good way to keep up with your body’s hydration needs is to stay on top of how much fluids you’re losing. There are many factors that impact how much an athlete will sweat during a winter workout, including the duration of exercise, temperature, body weight, and type of clothing.

Calculate Your Sweat Rate

An easy way to know how much fluid you typically lose through sweat is by calculating your sweat rate.

  • Before your workout, record your body weight without any clothes on.
  • After your workout, dry off and record your weight again.
  • During your workout, make a note of the type of fluids you drink, how much, and how frequently.
  • Subtract your pre-exercise weight from your post-exercise weight; then add the amount of fluid consumed to that amount. This number will equal your fluid loss during exercise.
  • Divide your fluid loss number by the number of hours you worked out. Then, divide that number by the number of hours you exercise.

This final number is your sweat rate, which will give you a better idea of how much fluid you need to replace after your winter workout.

Warm Yourself Inside and Out

Andy Blow, sports scientist and founder of Precision Hydration, advises athletes to dress warmly with plenty of layers, paying special attention to hands and feet. It might seem obvious, but dressing properly will keep your body temperature in balance by preventing too much blood from being sent to your core. Additionally, drinking warmed fluids ensure you stay warm and hydrated.

An easy way to hit both marks is with a sports drink designed to be warmed up and then stored in an insulated water bottle for easy access throughout your workout. Look for an insulated water bottle with a double wall of premium stainless steel, which will keep your drink warm for up to 12 hours (and cold for 24 hours in hot weather). Stainless steel is one of the best materials for a water bottle because it will never rust or leave a metal taste in your mouth. Plus, it's 100% BPA free and non-toxic, so you don't have to worry about chemicals leaching into your body over time.

Drink More Than You Think You Need

The best way to stay properly hydrated in high altitude, cold temperature environments is to drink as many fluids as you would when training in the heat, even if you don't feel thirsty. In cold, high-altitude climates, Stavinoha recommends 1 to 2 liters per day or 16 to 20 ounces per hour, which is the standard amount for endurance athletes training in the winter.

The type of fluids is also an important factor to consider. For long-distance running, athletes will need more carbs since the body requires additional energy to preserve heat and acclimate to elevation changes. Simply drinking water won't be enough, especially since H2O only replaces 50% of fluid losses. You also lose sodium through sweating, which is why we recommend filling an insulated water bottle with a sports drink that contains 460 to 800 mg of sodium per liter. This will ensure that your salts, carbs, and fluid loss is adequately replaced during training sessions.

Pre-hydrate and Rehydrate

For the best possible results during your training or workout sessions, pre-hydration is also extremely important. Not only does it impact your overall performance, but it also helps you avoid chronic dehydration, a particular concern if you participate in several high-intensity activities per day. One way to check if you are hydrating enough before exercising is by checking your urine color, which should be a light yellow shade. As a general rule, the National Athletic Trainer's Association recommends 500ml two hours before training.

Rehydration after training is also just as vital — it is essential for cardiovascular function as well as muscle repair. It will also help replace any loss of fluids through sweating. Once you know your sweat rate, you'll have a better idea of how much fluid you need to replace after a winter workout session.

Now that you have a better idea of how much fluid intake you need for optimal performance during the winter season, it's time to exercise, hydrate, smile, and repeat!