For those of you not going 'yay' and happy dancing on the spot at the mere thought of it, then some cooling and safety tips are clearly necessary. It is important to face facts and to know that we are all different. Some people thrive in heat, then freeze at the first bit of shade; some people feel like they're going to die in heat, but will happily run around in winter with a t-shirt on. Do not try to soldier on when the temperature is getting to you. Always pay attention to what your body is telling you, because your body has a very important job to do. That is to keep you alive, fit and healthy. You cannot gage what should be happening by looking at the person next to you. They have an entirely different body, with its own set up.
(I have a totally unverified and unscientific (as far as I know) theory on this. I think that some people are great in heat and and some great in cold, while some are night people and some are day people, for a reason. Back in the day, when we were all living in caves, this allowed human beings to have bright and alert sentries outside 24 hours a day, 365 days a year. Come rain or shine, dark or light, there was always going to be someone enjoying being out there. That's my theory anyway and I'm sticking to it.)
In addition to this, our bodies become attuned to our usual surroundings. Someone flying straight from a month in the North Pole into the heat of a Mexican jungle is going to feel unbearably hot. Someone arriving from the Sahara Desert to the same jungle would feel a bit cold. It takes a bit of time for our internal temperature gage to acclimatize to the new 'normal' heat. Once it does, then there will be fewer problems, until you jet off to yet another new climate.
Until your gage has realigned, then the symptoms that you may experience are all due to your body trying desperately to return you to the temperature back home. How it does this is downright ingenious, so please take a moment to pause, observe and applaud all that work done by your body's cooling and heating mechanism. After all, it keeps you alive.
As you start to heat up outside your body's comfort zone, then this cooling mechanism kicks in. At first, the hints are quite subtle. You might get a sudden urge to take off your cardigan or shoes. This naturally cools you down a bit. If you refuse point blank, then the physical manifestations begin. You will start sweating. Two things are going on here: cooling of your core temperature (major organs) and cooling of your surface temperature (skin). As you sweat, water from inside your body evaporates on the surface of your skin. This cools your skin. If this water is from the core, then it's taken all of that heat out, thus cooling down your organs. The more you sweat, the hotter you are. Someone literally drenched in sweat really does need to seek shade and fluids right now. Someone sweating to that level for over an hour needs to find medical attention, as extreme overheating can kill, hence the body making all of this fuss in the first place.
Around this time, your body will have gone from a suggestion that you might fancy a chilled drink, to making you feel like you (or someone) is going to die if you don't get a drink right now. As well as the drink introducing a cool temperature right through your core, it is also replacing all of those fluids that you are sweating out. However, it's not just water that you're losing in sweat, it's salt and minerals as well. Because of this, please be discerning in your choice of drink. Fruit juices, for example, will sort you out a lot faster than alcoholic, caffeinated or carbonated drinks. If you have an orange juice now, you will be able to get back to the mojitos a lot faster.
Just taking lots of fluids, while sweating profusely, will sort most people out. If it isn't happening fast enough, then the body brings out its major artillery. You will hurtle straight past the 'I need some shade' stage and into the 'I'm getting into the shade RIGHT NOW'. People in the grip of this will be close to tears or getting angry, because every neuron in their brain is screaming for shade. It's all good. It's keeping them healthy. As soon as shade is achieved, all will be well again.
If shade doesn't happen, then the next step is for the body to stop the person in their tracks. Our over-heating individual will become extremely lethargic and have no energy at all. Walking another inch is only going to happen if there is a definite guarantee of shade in that direction, because now they are using their last reserves of fuel and need to conserve it. Failing this, the internal temperature gage will be trying to get your body to lie down. You will feel light-hearted and/or very tired; you might progress to actual dizziness or the need to go to sleep. Worst case scenario, you will actually faint.
You can't really do much to help yourself now, so you're relying on the kindness of those around you. If you find someone in this state, then help them to cool down. Water or a damp cloth applied over the veins in your wrist, or at the back of the knees, or at the back of the neck, are all good for the short-term. These get coolness into the core very quickly. If the person is conscious, then give them water or, even better, fruit juices to drink. (There is a risk of vomiting, so look out for that.) If they have layers of clothing on, suggest and/or help them to remove the outer ones. Help them to get into the shade. Then all should return to normal again.
All of this is simply the body stopping any further exertion, to stop you getting even hotter; while allowing itself to shut down unnecessary, luxury add-ons, like the ability to think, talk and move. Right now, the body is only concerned with looking after the major organs and your brain. If it can keep those safe, then the rest can be fixed later. By now, our over-heating person will be pale, as blood is diverted out of their rosy cheeks into more important areas. They may have, perversely enough, cool, clammy skin in their extremities. Again because all of the body's resources are now with the major organs and brain. Try touching their torso, particularly around the chest area, and you find temperatures that you could fry an egg on. (Though obviously only do that if you know them very well and touching them in the chest area won't result in a court case.)
Finally, there will be nausea and/or vomiting. This is the body expelling any content from the stomach, in case it's poisonous and therefore causing more heat; however, it also happens with dehydration, which is certainly going to be present here. For a lucky few, the vomiting stage is the last resort, but it's the one that works. The body saves it until last, because vomiting isn't good for it. However, it is a good way for the body to extract a lot of heat from the core, which could well be the edge that it needs to realign. For the same reason, some people get an urge to go to the toilet, as the body empties the over-heating bladder and bowels. However, it won't choose this at the price of getting you to move.
Right now, the individual will be suffering from heat exhaustion. While it's still heat exhaustion, then most people won't require the emergency services being brought in. Just to recap there:
* Listen to your body. If it wants your jacket taking off or a drink, then obey it. It's keeping your temperature on the level.
* If you or one of your party is overheating: stop any exercise; remove clothing as appropriate for personal modesty; take it slow and steady, if you have to move; head into the shade or an air-conditioned area; sit down and rest; drink water and/or fruit juices; use water and/or damp clothes to the wrists, back of the knees and back of the neck; and just chill out for a bit.
* If symptoms persist, even after the treatment outlined above, then it might be worth calling in a doctor or medic. If they persist at that level for more than an hour, then definitely get them to hospital. This, however, is highly unlikely and more often than not indicative of deeper medical issues.
If, however, heat exhaustion is left untreated, then it will progress to heat stroke, which can be fatal. This is no time for messing around. If you or someone in your party has heat stroke, then call in an ambulance. In Mexico, you have a choice of three numbers, which will all summon an ambulance: 066, 060 or 080. (In some regions, particularly in the north of the country, 911 also works. However, this has transferred through an American switchboard and been redirected to the proper number.)
The symptoms of heat stroke start with those already outlined. But this time the person hasn't cooled down and now the brain is over-heating. Until now, the brain has been in charge. It's been the control centre that's ordered all of the life-saving devices, like sweating and suggesting a nice drink, in order to stop us getting to this point. Now the brain can't make any commands, as it's in crisis itself. The inner sanctum has been breached.
* The body's resources return to the extremities, instead of staying back to protect the core. The patient's skin becomes hot and flushed. It also becomes dry, because the brain has stopped telling it to sweat.
* The body can no longer cool itself with a variety of means, so its temperature rises. This can reach 41ºC (106ºF) or higher.
* The heating of the brain interupts normal service. Headaches begin, which may be followed by body twitches or all out seizures.
* Directionless, all of the body's normal responses are trying to happen all at once. This contributes to the seizures, but is also responsible for a rapid pulse.
* Unconsciousness quickly ensues, as nothing in that person's body is coping anymore.
If you find someone in this condition, all you can do is called for an ambulance, then try to cool the person down. Do not try to give them drinks, it's too late for that. They are far too deeply dehydrated, so will need special medically prepared hydrating fluids, often administered by drip. You might accidentally cause them to choke for your efforts. You could spray them with cool water; wrap them in a wet blanket; place them in a cool bath; fan them vigorously; sponge them off; and/or try to create some shade around them. If they vomit, then turn their head for them, because they will no longer have the motor control to do it themselves. The ambulance will arrive and the majority of people do make a full recovery, even from this stage of things.
Heat exhaustion and heat stroke are when things get extreme. Both of them can be headed off at the pass by paying attention to your body, whilst in Mexico. If you're feeling hot and thirsty, then find some shade and have a drink. You'll soon cool down enough to continue enjoying your day.