When the final of the 2026 men鈥檚 football World Cup kicks off in New Jersey this weekend, players can expect temperatures of over 30掳C (86掳F). Indeed, much of the tournament has been played in challenging conditions 鈥� like the high elevation and thin air of Mexico City鈥檚 Estadio Azteca 鈥� giving pundits plenty to chew over.

But one factor has been less discussed: humidity. High temperatures may be uncomfortable, but it is really the combination of heat and high humidity that can make a football match 鈥� indeed, any activity 鈥� physiologically unbearable. Humid conditions make it harder for our bodies to benefit from sweating, as the air is already laden with moisture, hampering our ability to cool down.

This impact of humidity is still underappreciated. One way of taking both humidity and heat into account is the wet bulb globe temperature (WBGT), a measure of heat stress used by sports organisations. As 快猫短视频 went to press, the most extreme match of this World Cup (Uruguay vs Cape Verde) had an estimated WBGT of over 33掳C (91掳F) 鈥� a level at which people are advised to suspend all outdoor activity. Most of us simply aren鈥檛 prepared for such conditions, as we explore here.

It is really the combination of heat and humidity that can make activities unbearable

Yet, if we understand the dangers of humidity, we can start to grasp the advantages of dry heat. We detail the many ways in which saunas and heat therapy can keep you healthy, from cardiovascular benefits to protection against Alzheimer鈥檚 disease. The key is that saunas operate at extremely low humidity, allowing us to sweat comfortably while reaping the benefits of getting decidedly hot.

Saunas aside, we should still be wary of extreme heat. With European heatwaves on the rise, the 2030 men鈥檚 football World Cup 鈥� to be played across Portugal, Spain and Morocco 鈥� is likely to see low humidity but temperatures of up to 40掳C (104掳F). With no sign of us cutting carbon emissions, the World Cups of the early 21st century may one day be fondly remembered as nice and cool.

When the sun is out, many of us reach for sunscreen, but myths and misinformation have left some people confused about when and how to use it, and how to ensure we still get enough vitamin D. , a skin cancer expert at QIMR Berghofer Medical Research Institute in Australia, has led clinical trials looking at the link between sun exposure and skin cancer, and sunscreen use and vitamin D. She also recently led the development of a new that considers how to balance the risks and benefits of sun exposure. Here, she lists five things that everyone should know about sunscreen.

Sunscreen should be used as a last line of defence

Many people think it鈥檚 OK to lie on the beach all day in a tiny bikini as long as they rub sunscreen all over their exposed skin and reapply it every 2 hours. They think sunscreen makes them bulletproof. But even if you apply the best sunscreen perfectly, it still lets some ultraviolet (UV) radiation through. If you鈥檙e out in the sun for hours, that gradually adds up to a dose that is big enough to cause skin damage. At that point, it doesn鈥檛 matter if you apply more sunscreen; the damage is already done.

People often assume that if they reapply sunscreen every 2 hours, they鈥檙e sort of starting the protection again, but that鈥檚 not how it works. You also need to protect yourself with a hat, sunglasses, rash shirt or other protective clothing, and stay in the shade in the middle of the day. Sunscreen should be considered a last line of defence for the parts of your skin that you can鈥檛 easily cover while you鈥檙e outdoors, like your hands and neck.

There is good evidence that sunscreen protects against skin cancer and wrinkles

The largest, longest-running study of sunscreen was conducted in the Australian town of Nambour. In 1992, 1600 people in the town were randomised to apply daily sunscreen or continue with their normal sunscreen use, which tended to be minimal. It found that those who applied the daily sunscreen were years down the track.

The researchers also created moulds of the backs of the study participants鈥� hands to look at damage to the surface of the skin. Those in the daily sunscreen group had compared with those who didn鈥檛. When they were followed up on in 2014, they also had .

The sunscreen to choose is the one you like wearing

It鈥檚 no good having sunscreen that sits in your cupboard and doesn鈥檛 end up on your skin because you don鈥檛 like the feel of it. If you鈥檙e going on a hike and you鈥檙e going to be out all day, it鈥檚 better to wear sunscreen with a high sun protection factor (SPF) of 50+. But it鈥檚 harder to get a high-SPF sunscreen that feels really nice, so if you鈥檒l be popping out for only short periods throughout the day, you can choose an SPF 15 or 30 sunscreen. Tinted sunscreens can offer the same protection as normal sunscreens, but only if you apply them thickly. But because these often make the skin look overly tinted, people tend to apply them too thinly. One option is to first put on a thick layer of normal sunscreen, then apply the tinted sunscreen on top of it.

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Chemical sunscreens, meaning those that contain organic ingredients such as octocrylene and avobenzone, work by absorbing UV radiation from the sun and converting it to harmless heat. Inorganic sunscreens, also known as mineral or physical sunscreens, contain zinc oxide or titanium dioxide particles. They are often reported to work by reflecting or scattering UV radiation, but they actually , like chemical sunscreens.

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Wearing two layers of sunscreen helps to achieve adequate coverage

You get the SPF listed on the bottle only if you apply 2 milligrams of sunscreen per square centimetre of skin, which is around in an average adult. But it鈥檚 really hard to apply this amount of sunscreen in one go. One day, I decided to measure it out exactly, and I couldn鈥檛 rub it all on; it was too much. So now, I apply one layer, let it sink in while I brush my teeth and do other things, and then a second layer, so I can apply the full recommended amount.

I was born in Armidale, Australia, in the late 1960s and didn鈥檛 wear sunscreen as a child, despite my pale skin. I鈥檝e since had three skin cancers removed, the first of which appeared when I was just 29. So now, I am careful to protect my skin.

If you鈥檙e diligent with sunscreen, you might need to take a vitamin D supplement

We recently conducted a trial called the Sun-D Study to see whether applying SPF 50+ sunscreen every day affects people鈥檚 vitamin D levels. We randomly assigned 639 people to apply SPF 50+ sunscreen as part of their daily morning routine on days when the UV index was forecast to reach 3 or higher, or to use it at their own discretion. After about a year, a 鈥� about 46 per cent compared with 37 per cent in the control group. If you wear sunscreen every day, I would advise taking a vitamin D supplement so that you don鈥檛 become deficient, especially in winter. I take one myself 鈥� they are cheap, safe and effective.

People with dark-coloured skin are at greater risk of developing a vitamin D deficiency. I recently led the development of a new that looked at how to balance the various risks and benefits of sun exposure. It brought together experts from many Australian universities and medical organisations, and it concluded that people with dark-coloured skin need to put on sunscreen only if they plan to spend more than 2 hours outdoors on days with high UV radiation levels. This is in recognition of the fact that melanoma incidence is 30 times lower in people with dark-coloured skin than in those with light-coloured skin, and that vitamin D deficiency poses a greater risk.

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The heatwave that swept Europe last week saw many temperature records broken, leading people to ask if extraordinary June heat is the 鈥渘ew normal鈥�. Unfortunately, the truth is that we are never going to have normal in our lifetimes again 鈥� just ever more extreme heat.

Climate scientists are continually warning of the need to prepare for hotter heatwaves, worse droughts, more flooding and rising seas. During heatwaves like the one just passed, the hottest and most humid ever seen in Europe, they might even get a little media coverage. But then the weather cools, the news agenda moves on and nothing is ever done.

We are currently on course for average global surface temperatures to rise by between 2.1掳C and 3.3掳C by 2100, and possibly even more. Even these alarming numbers are a little misleading because the oceans that cover most of the planet don鈥檛 warm as fast as the land. Average land temperatures are therefore going to go up by a lot more than the above numbers imply.

But what really matters to us is extreme weather, not the average. The projections for future extremes are already dire, and there are reasons to think that we are in for extremes even greater than those currently projected for a given level of warming. With uncertainties over the survival of the vital AMOC ocean current and the risk of a major glacier collapse, the only thing we really do know is that we must prepare for conditions far worse than Europe has just experienced.

We are on course for average global surface temperatures to rise by between 2.1掳C and 3.3掳C

It is possible to get through even worse heatwaves if all your infrastructure and systems are geared up to cope, but for most countries, this isn鈥檛 the case. The fact is, the world is changing fast and we need to change just about every aspect of our lives to adapt 鈥� our homes and offices, factories and schools, cars and trains, farms and gardens, and so on. But it isn鈥檛 happening. One day, after the tragic deaths grow too great to bear, we will ask why we did nothing to prevent them.