​​Summer has just begun, and the weather is already sweltering. Millions of Americans have experienced record-breaking heat waves in the past few weeks.

There's no question: When the weather is hot, it puts stress on your body. If you want to stay healthy as the temperatures climb, good hydration is key.

“Our body is made up of a lot of water. It's an essential part of how our body functions," says family medicine physician Shelby Gardner, MD. “Our cells, the blood flowing to all our different tissues and organs—a lot of that is water. Staying hydrated is a big part of how we stay healthy."

When you aren't taking in enough water, you get dehydrated. Your body gives you signs when it's running low on fluid. It's important to know those signs and what you can do to avoid dehydration.

Why is good hydration important?

Water is vital for your body to function. Overall, it makes up 60% of your body. Water is an even bigger part of specific organs. It's 73% of your brain and heart, 83% of your lungs and 79% of your muscles and kidneys.

Dr. Gardner says all your organs need enough water to work their best.

“Most of the time, our bodies do a really nice job of maintaining balance," she says. “But when the temperatures get hotter, and it gets more humid, we sweat more and start to lose fluid. It becomes harder for those mechanisms responsible for keeping that balance to stay in check."

Losing hydration impacts four areas of your body the most, Dr. Gardner says:

• Skin: Sweating pulls water from inside your body to the surface of your skin to cool you off. Sweating is necessary to control your internal body temperature, but it also draws water away from your organs.
• Heart: When you lose fluid, your heart must pump harder to circulate blood to all your organs. As a result, you will feel a faster heartbeat.
• Kidneys: Without enough water, your kidneys will concentrate your urine, increasing the content of salt and other waste products. This concentration can boost your risk of developing a urinary tract infection.
• Brain: Without enough hydration, your brain shrinks in size. You can experience headaches, confusion, mood changes and sleeping problems.

​Who's at risk?

Dehydration can affect anyone. However, Dr. Gardner says some groups are more at risk during hot, humid weather. These groups include:

• Babies and toddlers: Children sweat and get rid of moisture quickly, so they can lose hydration fast.
• Older adults: The mechanism that triggers thirst or lets older people know they don't feel well doesn't function as effectively as it does in younger adults.
• People who are pregnant or breastfeeding: Growing or breastfeeding a baby requires greater amounts of fluid, potentially leading to dehydration.
• People with certain medical conditions: For patients with heart failure, dehydration makes it harder for the heart to pump fluid to all parts of the body effectively. Consequently, their legs may swell, or they can develop an irregular heartbeat. For patients with diabetes, sugar pulls water from their bodies, causing excessive thirst and urination. As a result, they may not notice when they become dehydrated.

Dr. Gardner says people who spend long periods outside, such as maintenance workers, construction workers, farmers and people without access to air conditioning or indoor shade, are also at greater risk for dehydration.

​Early dehydration symptoms

Dehydration can cause a wide range of symptoms, depending on how much fluid you've lost. It can be difficult to tell if the signs are linked to your activity or dehydration. But you should pay attention to them either way.

The early signs of dehydration include:

• Being thirsty
  
• Dry mouth
• Light-headedness
• Muscle cramps
• Sweating
• Urinating less often

In fact, the color of your urine can let you know if you're getting enough water, Dr. Gardner says. Urine should be light yellow, relatively clear and nearly odorless. Dark, orange-colored urine that smells bad indicates you're dehydrated.

​Signs of severe dehydration

Dr. Gardner says over time, dehydration can lead to more severe complications, including heat exhaustion and heat stroke​. Both conditions require immediate action.

​Heat exhaustion

Symptoms: People experiencing heat exhaustion will sweat a lot. Their blood flow can't keep up with the body's needs, so they may feel tired, dizzy, shaky and nauseous. They can also get muscle cramps or a headache. In addition, their internal body temperature can rise to 104°F.

What to do: Move the person to a cooler place and loosen their clothing. Offer water and apply cool, wet cloths or towels.

​Heat stroke

Symptoms: Heat stroke is a medical emergency. It produces many of the same symptoms as heat exhaustion, but the person's internal body temperature can be higher than 104°F. They may also feel hot—but dry—to the touch, and they may have seizures.

What to do: Call 911 or take the person to the hospital immediately. Rapidly lower the temperature around the person. Loosen or remove their clothing. A heat stroke can be fatal, but most people fully recover without lasting problems.

​Protect yourself

Fortunately, there are several things you can do to avoid dehydration. To protect yourself, Dr. Gardner recommends:

• Staying ahead of thirst: Drink water regularly during the day. If you feel thirsty, you're already dehydrated.
• Drinking more than 8 cups a day: Women should drink roughly 11.5 cups of water daily. Men need approximately 15.5 cups.
• Giving sports drinks a try: If you're exercising, consider a sports drink with electrolytes to help your body recover.
• Thinking beyond water: You can get water from a variety of sources, including watermelon, tomatoes, berries, grapes, soups and other foods with a high liquid content.
• Limiting alcohol and coffee: Alcohol and caffeine can make it harder to recognize dehydration.

And, if you're active outside, don't forget to rest frequently, she says.

​“If you know you're going to be doing a lot of vigorous activity outside on a warm day, take a break every 15-20 minutes," she says. “Relax and take several small sips of water over time. That will help you feel better in the long run."​