Water makes up 60 percent of our bodies and 75 percent of our brains, according to WebMD. Staying hydrated is critical for every cell and system throughout the body.

UL’s sponsored LPGA golfers[KR1] , who have been competing during this summer’s record-breaking heat, understand how important it is to hydrate properly, which is why you’ll often see them taking sips of water throughout play.

After all, even 2-percent dehydration can cause significant problems performing mental tasks, reports a recent analysis of more than 30 previous studies. A statement by the study authors notes that, “just two hours of vigorous yard work in the summer sun without drinking fluids could be enough to blunt concentration.”

To keep yourself safe and hydrated even on hot days, be sure to:

1. Know when to stay inside. When the heat index, which takes into account humidity plus temperature, hits 91 degrees F (and can rise by 15 degrees higher than the official index in direct sunlight), try to avoid outside exertion; that’s when the Occupational Safety and Health Administration recommends employers implement precautions. This threshold may be lower for people 65 or older, or those who are overweight, have heart disease/high blood pressure, or who take medications that affect heat tolerance, says the Centers of Disease Control and Prevention (CDC).

2. Understand that dehydration can happen fast. Mindy Millard-Stafford, the study author and a professor in Georgia Tech’s School of Biological Sciences, says, “If you weigh 200 pounds and you go work out for a few of hours, you drop four pounds, and that’s 2 percent body mass. With an hour of moderately intense activity, with a temperature in the mid-80s, and moderate humidity, it’s not uncommon to lose a little over 2 pounds of water.”

3. Monitor your hydration. WebMD recommends that instead of following the eight 8-ounce glasses per day myth (which is not backed in science), instead drink enough water that you need to empty your bladder every two to four hours.

Note, you’re already dehydrated if you experience dehydration signs, such as weakness, leg cramps, fatigue, confusion, decreased skin elasticity (turgor), rough, dry or coated tongue, fever, weight loss and, at times, restlessness and agitation. At that point, focus on rehydrating.

4. Protect yourself. Although it’s challenging to come up with fluid guidelines for everyone, since fluid needs vary based on health, age, diet, activity level, weight, etc., the CDC recommends that for moderate activity in moderate conditions, outdoors workers drink 1 cup of water every 15 to 20 minutes.

Athletes should drink before thirsty, advises WebMD, and, in general, drink 2 cups of fluid two hours before the activity, 4-6 ounces every 15-20 minutes during exercise and 16 ounces after – more if it’s hot. Add an electrolyte tablet or use a sports drink if exercising for an hour or more. Weighing yourself before and after exercise is more precise. Rehydrate with 20 ounces of fluid per pound lost.

Elderly people often are more susceptible to heat and dehydration for many reasons, such as age-related reduced sense of thirst, as well as certain medicines, according to The Baltimore Sun. So even when it’s not hot, they should sip fluids throughout the day, and get hydration through foods like include soups, broths, and watery fruits.

5. Take regular breaks. Exerting your body increases your body’s temperature. Once your body temp gets too high, you start feeling the symptoms of a heat illness, which can quickly escalate and become life-threatening. During extreme heat, the CDC recommends rescheduling work to cooler times of the day, taking of frequent breaks in a shaded or air conditioned area, wearing reflective clothing or water-dampened cotton clothing, and donning cooling vests with pockets for cold packs.

6. Use sunscreen of 30 SPF or higher, and wear sunglasses, a hat, and long-sleeve UV-rated clothing, while trying to avoid direct sunlight.

7. Don’t drink too much water, which raises the risk of hyponatremia – low sodium blood concentration. Learn more here.

8. Recognize the signs of heat illnesses. Know these signs, along with heat illness first aid.

Hydration is important all times of the year, even in the middle of winter, but it’s easy to quickly get dehydrated when spending time outside in the heat. All times of the year, as noted above, make it a habit to drink enough water throughout the day to have to use the bathroom every two to four hours. You’ll be more alert, and your whole body will function better when you stay hydrated.