50 degrees Celsius at noon. Melting roads. Out-of-control wildfires.
This is summer for parts of the northern hemisphere right now.
The searing heat has claimed many lives, from Crete to California, and New Delhi to Mecca, as temperature records have tumbled over the past month.
Sunday 21 July was the hottest day since at least 1940 according to the Copernicus Climate Change Service.
But while Greece shuts the Acropolis and people suffer third-degree burns from footpaths in Las Vegas, it’s all blankets and heaters in parts of Australia.
We’re having a frosty winter, with a few Antarctic polar blasts, and many Australians from chillier regions will seek a temporary reprieve from the cold and head overseas for a “Eurosummer” or US vacay in July and August.
But the extreme temperature change between take off and landing is a huge test for the body, so preparing ahead of your trip may help you to stay safe in the heat.
Making the switch from cold to hot
If you live in southern Australia and travel to southern Europe or some parts of the US around this time of year, you can expect up to a 30-degree difference in maximum daily temperature.
That’s a huge shock to the body, says Harry Brown, a post-doctoral researcher at the University of Canberra who specialises in seasonal acclimatisation.
Coming from winter, you will have a low tolerance to heat, and the physiological adaptations the body uses to stay cool, such as sweating more profusely, won’t instantly activate when you touch down.
“It means a normal task like just a bit of sightseeing in Italy will increase our heart rate a lot more than if we were just walking around Canberra,” Dr Brown says.
While it’s a myth your blood gets thinner when you swap cold weather for hot, your blood vessels do need to change size to cope with the temperature change.
Instead of constricting to minimise heat loss, they dilate, bringing more blood to the skin and releasing heat.
Humans can acclimatise — we do it every time the season changes — but it normally happens slowly over several months.
We can, however, build up our tolerance more quickly through repeat exposures to heat, and safely pushing ourselves to increase our physical activity, which raises our core temperature and blood flow to the skin.
It’s a bit like what the Olympians have been doing in preparation for Paris.
“This constant disruption to our core temperature will prompt the body do things differently,” Dr Brown says.
Special heat adaptions will be “turned on” and allow us to endure high temperatures with less risk of heat stroke and death.
The key signs someone is acclimatised include:
- having a lower heart rate and core temperature when active
- improved sweating (earlier onset of sweating, loss of more millilitres per hour, and reduced loss of electrolytes)
- a higher volume of blood plasma, meaning the heart doesn’t need to work as hard to pump blood around the body.
But Dr Brown says it can take up to three months for someone to fully acclimatise if they aren’t doing a specific regime for heat acclimatisation.
And even if you’re a physically fit person, meaning you’re more heat tolerant to begin with, acclimatisation can still take 14 days.
By then, it’s possible your Euro trip will be coming to an end.
So with acclimatisation likely impossible on a short holiday, it may pay to use some heat mitigation strategies to help you not only survive the conditions, but actually enjoy your trip.
“People pay a lot of money to get over there so they want to make the most of it,” Dr Brown says.
How to prepare before you go
Don’t just think ‘I’ll be right’ when I get there.
If you have any pre-existing conditions or health concerns make sure you see a GP before you depart so you can discuss risks.
“Don’t just leave it to chance, talk to your pharmacist or doctor because pre-planning goes a long way,” Dr Brown says.
If you’re generally fit and healthy though you could try to give your body a head start.
Matthew Brearley is a heat stress consultant and works for the National Critical Care and Trauma Response Centre where he prepares Australian medical personnel for overseas deployment.
He says if you’re up to it, you could try and get your sweat on by doing some physical exercise in warm conditions in the lead up to your holiday.
Whether it’s a heated yoga class or just putting on extra jumpers for a long walk, the idea is to raise your core temperature and get you sweating, which helps wake up those heat-coping adaptations.
Dr Brearley says a lot of his medicos do Bikram yoga to prepare for work in hot, humid environments.
“They find it helps them a lot.”
What to do once your holiday starts
Once the holiday begins, be amenable to adjusting your travel schedule — it could save your life.
Don’t stick to set plans to do a hike on a specific day if the mercury is set to reach 44C.
“I know it’s hard because people feel they have one chance to do something and they’ll never be back here, so they take the risk and ignore the messages their body is giving them,” Dr Brearley says.
“They will be really motivated to get to a certain viewpoint or landmark and that supersedes how they feel and they end up perishing.”
In June, at least 10 tourists went missing or died in Greece after going walking in sweltering heat. One of those people was British doctor and author Michael Mosley.
“We make really terrible decisions when we’re hot. We tend to underestimate the risk,” Dr Brearley says.
“Plus you’ll likely be jet-lagged from the flying, so fatigue is another risk factor when you’re out in the elements.”
Staying hydrated is essential, but it’s not a substitute for resting in the cool.
“Your body temperature will cause the harm and lead to a possible heat stroke,” Dr Brearley says.
Think of heat in your body as a see-saw. On one side, you have the heat being produced by your body, and on the other, the amount of heat you can lose.
If heat production outweighs loss, you need to decrease your activity level.
“That means walking very, very slowly if it’s really hot, which probably isn’t going to allow you to do what you want to do without prolonging your overall exposure,” Dr Brearley says.
So, if possible, seek out air-conditioning, especially in the hottest parts of the day.
A small misting bottle that fits in your bag is also an easy way to help you thermoregulate as spraying water on your face, arms and legs will increase evaporative cooling of the skin.
“That’s especially good when there’s a power outage or you’re between accommodation,” Dr Brown says.
Dousing your feet in cold water is another good cooling technique if you’re showing any signs of heat exhaustion which include nausea, headache or muscle cramps.
And if you have kids, put a damp muslin cloth over their stroller instead of a dry one. While it might provide some shade, a dry cloth can increase the temperature inside the stroller by 4C.
Should we reconsider travel at this time?
As global temperatures continue to rise, summer in the northern hemisphere is going to become increasingly dangerous, Dr Brown says.
Young children, those over the age of 65 and anyone with underlying health conditions, particularly cardiovascular disease or renal disease, will be most vulnerable to drastic temperature changes.
And some countries don’t have the infrastructure to deal with extreme weather and may have limited air-conditioning.
“It comes down to personal planning. Think about whether it’s going to be worth going at that time of year if you’re not fit and well,” Dr Brown says.
Older people often sweat less so have more trouble cooling down. Certain medications, like those taken to control blood pressure, can also be dehydrating as they make people urinate more.
But, Dr Brearley says, even people who are physically fit should think carefully about what they do.
“Look at the conditions and ask yourself, ‘Am I up for that?’ If not, postpone or re-evaluate your plans based on the environment.”
Even if the forecast temperature seems tolerable, the humidity can tip you into the danger zone as it makes it harder for sweat to evaporate from your skin, which makes it harder to cool down.
Travellers should keep up to date with local weather warnings, Dr Brown says, and check Smart Traveller for health advice specific to your holiday location.
Coming home
Returning to the Australian winter after weeks in the heat will be a bit of a shock to your body, but certainly not dangerous.
Your thermal perception will be different, so you’ll feel colder and perhaps more uncomfortable than before you left.
But it’s generally easier for the body to generate heat than lose it.
“Layer up and trap the heat,” Dr Brearley says.
“And obviously be smart and give yourself time. I wouldn’t going to the alpine region just after coming back from Phoenix.”
Get the latest health news and information from across the ABC.