The most effective and cheap ways to cool your body during a heat wave, according to scientists

• Unseasonable heat is already being felt around the world.
• Insider asked two scientists for simple, effective, and cheap ways to cool down.
• Regulating your diet, fluid intake, and cooling key parts of the body can be a big help.

Unseasonable heat is already hitting the globe. By the end of May 2023, the Pacific Northwest had already been hit by a heat dome and heatwaves were reported in Asia.

"May 2023 was quite warm across the contiguous U.S., ranking as the 11th-warmest May in the climate record," the National Oceanic and Atmospheric Administration said in a post June 8. 

"The month also wrapped up a rather warm year so far."

Insider asked two scientists evidence-based advice on how to keep cool without breaking the bank. 

Put your hands or feet in cold water

In extreme heat, the body opens up the blood vessels that are close to the skin. Blood carries heat from inside the body to the surface, where it can benefit from the cooling effect of sweat evaporating.

To stay cool easily, focus on parts of the body with lots of blood vessels: hands, wrists, feet, ankles, and armpits.

Speaking with Insider in 2022, George Havenith, Professor of Environmental Physiology and Ergonomics of Loughborough University, recommended putting cooling pads on those areas, or dunking them in water.

If you can, a swim or a cool bath or shower is also very effective.

You can also spray your skin with water or wet your t-shirt, said Havenith. This cools the skin down like sweat but without costing the body any of its own moisture.

Eat light meals 

Eating lighter meals like salads is another common-sense bit of advice with scientific backing.

This is because light foods require less energy to digest, and produce less heat inside the body. "The more complex foods will ultimately actually produce more heat in the body as they're broken down," said Owen Jeffries, lecturer in Sport and Exercise Physiology of Newcastle University, in 2022.

However, Jeffries warned that hot weather can cut your appetite, so it's important to make sure you're eating enough.

Use an electric fan, but be careful in very hot weather 

A fan helps cool you down by helping sweat evaporate faster. It can be just as effective as air conditioning and is much cheaper.

"It's perfectly safe — and preferable to air conditioning — to use an electric fan up until 35°C," (95°F) said Jeffries. 

"What you can do is in terms of simple measures, put a bowl of ice cubes in front of the fan," said Havenith.

"You can feel that the air is cooler when you do that," he said. 

In very hot weather, like temperatures over 95°F, the World Health Organization recommends against using a fan.

In dry heat, sweat is already evaporating at maximum efficiency. All a fan might do is blow more hot air on you.

And in humid heat, the air has so much moisture that sweat can't evaporate, which could render it ineffective.

Unless you're exercising, sports drinks won't rehydrate you quicker than water — but milk might.

Havenith and Jeffries pointed to a 2016 study on rehydration that compared several drinks.

It found that sports drinks, sparkling water, and Coke were no better than water.

Skimmed milk, whole milk, and orange juice, however, were marginally better at rehydrating the body.  

The downside of sports drinks is that they contain "a vast amount of sugar," said Jeffries. Unless you are exercising, that sugar doesn't get used and will be converted to fat.

Coffee was surprisingly good at rehydrating in small quantities (though very slightly worse than water).

Both scientists pointed out that tap water does the job, which is by far the cheapest option.

Drink before you feel thirsty

People start getting thirsty after losing 2% of their body fluids, said Havenith. It's better to drink before that happens.

You can check your pee to know if you're dehydrated. "If that gets darker, that's a clear sign that you're not drinking enough," he said. 

"It's better to sip water throughout the day rather than drink large volumes at a time," said Jeffries, because large intakes are likely to end up going to the bladder and quickly leaving the body.

Also, make sure you don't overdrink, which can itself be dangerous.

Very cold drinks work, but can also make you sick

Studies show that drinks like ice slushies can cool down the body, said Jeffries.

But they can be counterproductive if the body reacts badly to the sudden change.

"If you drink cold water, you have to always make sure that your stomach and your intestines don't get upset,"
 said Havenith."If that happens, you could get diarrhea, throw up, you would lose a lot of electrolytes."

Careful with exercise 

In hot weather, it's advisable to avoid strenuous exercise, unless you've specifically trained for the heat.

"You have this competition between the muscles and the blood flow to the skin," said Havenith. 

Oddly, people who exercise regularly can be at higher risk of heat exhaustion because of they are overconfident and push past their limits, said Havenith. 

"Typically, the very fit person will do more. And that's why it can't often be the very fit people that run into trouble."