How to survive a heatwave

How to Survive a Heatwave (On a Boat!)

Did you know that 2022 was the hottest year on record in the UK? And that June 2023 was the hottest month in the UK ever? Today it has been announced that July 2023 has broken the record for the world’s hottest month ever recorded! Understanding how to survive a heatwave is a lesson we all need to learn fast.

We’ve spent most of our cruising life in hot countries

We bought SY Esper in Turkey and spent the first three years living aboard her in the Eastern Mediterranean. The summer temperatures, particularly in August, often topped 40°C. One memorable year, it reached 50°C. With very little wind, we cooled down in the sea and stayed under the shade during the day. One of the discoveries we made at that time was that we developed cramp if we did not add salt to our diet. Coming from a cool climate (where we never cooked with salt because it was regarded as bad for us) this was a happy result!

We arrived in Kerala in April, pre-monsoon and the hottest time of the year. Over the next few weeks, temperatures rose from 35°C to 40°C. But it was the unbearable high humidity which done for us!
The building workers on the bank opposite disappeared at lunchtime, arriving back at work in the evening. We’d see the welding lights sparking and hear the clanging of tools. We were with six other boats, and within the first few weeks ALL bought air conditioners.

How to Survive a Heatwave

In Thailand, Malaysia and Indonesia, where we have been sailing since late 2013, temperatures have remained between 29°C — 34°C. It is not so hot as other places we have sailed, but underneath the midday sun and with high humidity it can be unbearable at times.

What Is Heatstroke And Why Should We Take Action To Avoid It?
  • At best it’s painful and debilitating, with some symptoms that can last for weeks!
  • At worst heatstroke can kill you

Heatstroke occurs when your body stops being able to control its own temperature. The USCDC (“Centers for Disease Control and Prevention”) explains:

“… the body’s temperature rises rapidly, the sweating mechanism fails, and the body is unable to cool down. When heatstroke occurs, your temperature can rise to 106°F (that’s 41°C to the rest of us) or higher within 10 to 15 minutes.”

If that occurs and we fail to cool down, our cells will literally melt from the inside out.

How to Survive a Heatwave
Keeping cool in the water…

Over 65s, under 5s and those with some diseases (like diabetes) are most vulnerable to extreme temperatures. But it is important to remember that heatstroke can kill any of us, including fit and healthy adults.

Sunstroke is another term for heatstroke. Sunburn is not always a symptom of heatstroke, but heatstroke can easily become a symptom of sunburn.

How Do We Stop Our Bodies From Overheating?

Our body works hard to maintain homeostatis and keep its ideal temperature of around 37°C. As warm-blooded mammals, our core temperature does not change unless threatened by temperature extremes. These cause our body’s regulating systems to fail.

So, how do we stop overheating in higher temperatures? In a word: SWEAT

When we sweat, the moisture evaporates from our skin and carries the heat away with it, lowering our temperature. But in our natural world, there are two main threats to the body’s natural cooling system:

  1. Heat
    • When the outside temperature is too hot (the received wisdom is that this can be anything from 31°– 35°C) our bodies pour sweat onto the skin. But it has no time to dry and evaporate away from the body before more sweat arrives, and we begin to overheat.
  2. Humidity
    • If the air is too humid, there is already too much water in the air for our sweat to evaporate effectively. That is because the air can hold no more moisture. Once again, this stops our body’s natural cooling system from working.
How to Survive a Heatwave
Liz wrapped up like a pirate

What Are The Effects Of Heatstroke?

A simple experiment for the BBC World Service reveals the effect of increasing temperatures in a controlled environment. (If the link doesn’t work, search for “BBC: The Real Story, Surviving Extreme Heat” wherever you get your podcasts.)
These are the results after an hour.*

Heartbeat increase (beats per minute):

  • 21°C 54 bpm
  • 35°C 81 bpm
  • 40°C 87 bpm

Water loss:

  •  ½ a litre

Ventilation rate (breathing) increase:

  • 21°C 9L air per min
  • 40°C 17L air per min

*Humidity was set at 50%. The presenter is a man in his early middle age (not an athlete) who remained seated throughout the tests.

These results show just how much more work our bodies are doing (even without doing any exercise!) to try and preserve the core temperature. And they go some way to explaining why we are so knackered after being outside all day over here in SE Asia, particularly if walking and adventuring.

How to Survive a Heatwave
Stay out of the sun

How does humidity make it worse?

Humidity makes us tired, uncomfortable and irritable. With so much moisture in the air, it is more difficult for the body to maintain homeostatis. This is because humidity stops the crucial evaporation process from removing sweat and heat, causing our body temperature to rise faster than it would in a dry climate.

At Penn State Uni they are testing relative humidity rates on the human body. The results give us the critical limits of heat and relative humidity:

  • 36°C – 65%
  • 42°C – 40%
  • 50°C – 12%

RESULT: Confirmation that if humidity is low, our bodies can cope with higher temperatures. But once over the critical limit we are in danger of suffering heatstroke, unless we take measures to mitigate the threat.

BBC Report: How hot is too hot for the human body?

The high temperatures we are seeing now in the world are compounded by high humidity in many places. So it may be only 35°C on holiday, but if the humidity is over 65% (as it is in India or South-East Asia) we need to take extreme care.

What are the signs of heatstroke?

  1. Excessive sweating
  2. Muscle cramps
  3. Dizziness
  4. Increased heart beat
  5. Headache
  6. Vomiting and nausea
  7. Diminishing brain function
  8. Fainting
  9. Coma
  10. Organ failure (kidneys and heart)

How to avoid Heatstroke

  • Keep drinking fluids
    • Water is best
  • Add electrolytes* to replace lost body salts (a balanced diet should do this anyway)
    • Limit caffeine — including coffee, energy drinks (high in sugar and caffeine) and tea. Might be OK if they’re a regular part of your diet)
    • No alcohol (it’s a diuretic, EVEN BEER!)

*All cruiser first aid kits should include sachets of electrolytes

  • Eat hydrating foods
    • fresh fruits and vegetables
    • soups and porridges
  • Limit highly thermogenic food (foods that are harder to digest than others) — especially red meat, spicy foods containing cayenne and ginger, sweet potatoes, whole grains.
  • Cover your head, neck and face with a hat or scarf
  • Cover up with lightweight, loose clothes
  • Stay in the shade and avoid direct sunlight
  • REST (do no exercise)
  • Don’t get sunburned! (“it can knock out our ability to thermally regulate (functionally sweat) our bodies for up to 2 weeks”)
  • Use fans
  • Air con! (Not good for the planet, but that’s a whole other topic).

How to avoid Heatstroke On A Sailboat

All of the above

  • Open all the hatches to get a breeze through the boat
  • Use shades or curtains to keep out the direct sunlight
  • Get out to anchor. Use that breeze to cool the boat (and you!)
  • Cover up the boat with awnings
  • Use the wind to keep you cool, but remember the sun can burn your skin and still make you ill.
  • Sail – BUT ensure you cover up and wear sunscreen because sunburn is potentially dangerous too
    Get off the boat and go to a hotel, restaurant or shopping mall with A/C!
  • Sunburn:
    Sunburn is a BIG danger for cruisers — it’s not always a symptom of heatstroke.
    Use all the same avoidance tactics for heatstroke, and constantly top-up the suntan lotion.
    Over-exposure to the sun can cause skin cancer.

What To Do If You Think You Have Heatstroke?

  • Get into a cool place
  • Remove all unnecessary clothing – let the skin breathe, and the sweat evaporate
  • Steadily sip a rehydration drink, or cool water with electrolytes, or just plain water if that’s all you have.
  • Cool your skin – cold water from a spray or sponge will help
  • Get in front of a fan
  • Cold packs, wrapped in a cloth placed under the armpit or on the neck is good
  • Rest and stop all exercise

Seek medical aid if:

  • still unwell after 30 minutes of resting in a cool place, being cooled and drinking fluids
  • there’s a high temperature
  • the skin is hot and still not sweating
  • the heartbeat is not slowing
  • breathing is still fast, or there’s a shortness of breath
  • becoming confused, with a lack of coordination
  • there’s a seizure or fit
  • there’s a loss of consciousness

Check out the video episode on YouTube
Or listen to the podcast.

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