Many people are out and staying active in the spring sun, but with the mercury rising, it’s a good idea to know what your body needs to withstand the heat.

Water is the most essential element the human body needs — for a variety of reasons.

“In terms of macronutrients — such as carbohydrates, protein and fat — water is right up there,” said Suffolk Family YMCA Health and Wellness Director, Shannan Gormley. “The human body can go two weeks without food but only 72 hours without water. It’s a key component to sustaining life, and the hotter it gets the more you need.”

Gormley explained the body is 60 percent composed of water — the rest being muscle, tissues and fat mass.

“Water is important because it not only helps you maintain the structural integrity of all your tissues — which keeps your body running properly — but also ensures your metabolism runs properly and supports life functions,” Gormley said.

While water has several functions in your body, one especially important job is helping to cool you in warmer weather.

“The body’s entire cooling mechanism revolves around a person being hydrated,” Dr. LuAnne Lewis said. “When the body wants to cool, then it sweats, and if someone isn’t hydrated enough, the mechanism can’t work.”

A sure sign it isn’t working is if you’re not sweating when you ought to be.

“Fatigue, dizziness, nausea, headache and abdominal cramps are all bad signs,” Lewis said. “Those, combined with not sweating, are all signs a person is going in to heat exhaustion.”

The next step from heat exhaustion is heat stroke, which can be especially dangerous.

“One you starting getting neurological symptoms — like hallucinations — it’s time to go to a doctor and get help,” Lewis said.

Certain medications — such as antihistamines or diuretics— can put you at risk for fluid loss.

And while bundling up to sweat more may be popular, it can put you at risk for health complications — even a heart attack.

“It’s like wrapping your head in a plastic bag,” said InMotion Dietician Brooke Mercedes. “It’s just not a healthy practice. Your temperature rises because you’re speeding up your body’s functions. All you lose is water weight, though, and you will gain that back.”

Mercedes explained that the hotter your body is and the less you allow it to cool, the more it impairs your performance level.

When your body reaches an internal temperature of 105 degrees, it begins to impair your cells, and at 107 they begin to die.

Something that can have the same effect by not allowing your body to cool itself is the humidity.

“When the humidity is high, the body can’t sweat,” Gormley said. “It can’t cool off, because the sweat can’t evaporate off the skin.”

In the event you end up with heat exhaustion, it’s recommended to shed as many layers as possible, drink water and get in a shower or under a hose.

When you’re able to make it to the scale, “for every pound you lose while exercising, drink at least 16 ounces of water to replace it,” Mercedes said.

And while it might not be the most appeal drink to some, it’s not easily replaced.

“Stay away from energy drinks,” Mercedes said. “If you’re a heavy sweater, you need to replenish both the water and the sodium in your system. G2 and Gatorade are best.”

“So far as Gatorade goes, it’s made for athletes who are doing high intensity activities for prolonged period of time,” Gormley said. “Unless you’re sweating a lot, you don’t need it, and in most cases it’s just excess calories.”

And if plain old water bores you, “Try some flavor packets,” Gormley said. “Whatever it is, make sure you’re drinking at least 6 to 8 cups of it a day.”