Summer is *almost* here and it's already getting crazy hot and humid. For some reason, I tend to gravitate toward VERY hot places, and happen to go there during the hottest time of year. The most extreme example was heading to the Sahara in August!I learned a lot from the cultures who have thrived for thousands of years in those insanely hot places, and now I'm sharing what I've learned.
First Some Science!
A crucial part of staying cool is understanding how heatFirst Some Science!
is transferred and how our bodies self-regulate. I want you to imagine that you are a little campfire. Why? Your body creates heat. What we have to do in summer and winter is figure out how to either hold onto that heat (in winter) or get rid of it (in summer). Imagine you're in a cabin with a nice little fire in a small fireplace. It's snowing outside. Do you want the cabin to be small or big? A little fire can warm a little cabin, but not a big one, so in winter we need a small cabin. Now let's imagine it's a hot summer day, and we've got that fire going. Now, we want our cabin to be big, and maybe we'll open a few windows and turn the fans on to try to let that heat out. Remember, putting out the fire means we are no longer alive, so all we can do is adjust the size of the room. This blog post is how to accomplish that.Heat moves in 4 ways:
- Conduction: The process by which heat or electricity is directly transmitted through a substance when there is a difference of temperature between adjoining regions, without movement of the material.
AKA: touch cold things, don't touch hot things
- Convection: the transfer of heat by the circulation or movement of the heated parts of a liquid or gas
AKA use wind and water to take heat away from your body. - Radiation: the complete process in which energy is emitted by one body, transmitted through an intervening medium or space, and absorbed by another body.
AKA: heat from the sun, body heat. Stand close to cool objects, stand far away from hot objects or put a barrier between you and the hot object. - Evaporation: water molecules heat up until they have enough energy to transform from liquid into gas- effectively 'transferring' that heat into the surrounding atmosphere
We'll utilize conduction to transfer heat out by touching cold things- like ice and shaded rocks. When I was in Morocco, I would find a cold tile floor in the bottom of a building and lay on it- letting it suck away my body heat. We'll prevent conduction by not touching hot things like sun baked black cars.We'll use convection to transfer heat out by swimming in cool water and standing in front of moving air.
We'll help our bodies radiate body heat by wearing thin, loose fitting, minimal clothing. We'll prevent our bodies from absorbing radiant heat by getting out of the sun and staying away from objects that radiate stored heat (like concrete buildings and black top parking lots)
The Science of Sweat
When it's hot, we sweat. Our bodies push a combination of water, salt and minerals out our sweat glands an onto our skin. When those molecules get enough heat energy from our skin, they evaporate, effectively 'taking' that heat with them. This process is not 100% efficient, and is very dependent on the humidity of the environment. In a hot and humid environment, like a jungle, sweat just doesn't work very well to cool us off, and instead we end up with soaking wet clothing. This is why it's so important to wear fabrics that help that water evaporate as much as possible- which I'll get into later.
Portable, personal shade: You can also carry your shade with you by using an opaque UV blocking umbrella. I have a friend who hikes with one. It's hilarious, but he is definitely cooler than us.
We'll help our bodies radiate body heat by wearing thin, loose fitting, minimal clothing. We'll prevent our bodies from absorbing radiant heat by getting out of the sun and staying away from objects that radiate stored heat (like concrete buildings and black top parking lots)
The Science of Sweat
When it's hot, we sweat. Our bodies push a combination of water, salt and minerals out our sweat glands an onto our skin. When those molecules get enough heat energy from our skin, they evaporate, effectively 'taking' that heat with them. This process is not 100% efficient, and is very dependent on the humidity of the environment. In a hot and humid environment, like a jungle, sweat just doesn't work very well to cool us off, and instead we end up with soaking wet clothing. This is why it's so important to wear fabrics that help that water evaporate as much as possible- which I'll get into later.Putting the Science into Practice
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| Alex, Tony and I are annoyed at the fake shade of this umbrella |
Get in the Shade- (duh) But really, get into some REAL shade!
Its real shade a thing? Yes, because there is this deceiving thing I call fake shade. It looks cool and inviting but when you get over there to chill out you find that it's like an oven under there! This happens because whatever is creating the shade (I'm looking at you blue tarp!) does not effectively block light. The Bedouins in the Sahara lived in black tents made from woven camel hair. Sounds hot right? It isn't. Its nice and cool under there. Copying the people who live in one of the harshest environments on the planet is probably a good idea. Luckily for us, we don't have to haul around a camel hair tent. Get a silver / reflective / opaque tarp and bask in coolness. Make sure you leave plenty of room above your head and point the opening of the tarp into the wind to get maximum airflow. |
| One of my coworkers with his hiking umbrella |
Portable, personal shade: You can also carry your shade with you by using an opaque UV blocking umbrella. I have a friend who hikes with one. It's hilarious, but he is definitely cooler than us.
Wear a BIG dorky hat
I know, they're super lame. You either look like a dork or an old lady. A big dorky hat puts your face is in the shade. Shade is cool. Just make sure your hat provides your face with real shade and none of that shady fake shade. (see what I did there?) My favorite ugly hat is made from a cool white polyester for the top part to reflect heat, and under the brim is a dark gray fabric to block out the sun and bounce reflections off the water into my face. I wear this full brimmed hat
for kayaking and for hiking I wear this one
because it doesn't interfere with my backpack.
for kayaking and for hiking I wear this one
because it doesn't interfere with my backpack.
Get Wet
Jump or dive or wade into the largest, deepest, coldest body of water you can find. Water is almost always cooler than the air. Generally, the deeper and larger the body of water, the cooler it will be because the sun can't heat it up as quickly. Watch out for rocks and sharks.
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| After an insanely hot and humid day in Hong Kong, it was a relief to sit in freezing cold, rushing water. |
Be Lazy
Not all the time, just during the hottest part of the day. The cultures in some of the hottest places on earth set their schedules so that everyone can lay around and nap between 11am and 3pm. You make your little fire bigger by moving around and exercising. Get your work done early if you're a morning person, or grab a good headlamp and get to work after the sun goes down. Personally I think that early morning is better because it tends to be cooler. The environment around you has had time to cool off overnight, while after sunset the ground will still be quite warm and will radiate that heat up to you. When I worked in Oman teaching outdoor ed, we altered our schedules so that our students could sit in the shade and nap between 11am and 2pm. If you travel to UAE and Oman, you'll find that shops and restaurants close between 10 and 3.
Dig Down
Have you ever noticed how dogs will dig a hole and sit in it on hot days? The dirt under the surface of the ground is several degrees cooler than the top. They're digging to where it's cooler and then using conduction to get rid of their body heat.
My personal fave for 'digging down' is going caving, but that is an extreme example. I had some students once dig a hole at the beach and get into it. It was definitely cooler in there than out on the sand! Basements are always cooler in the summer than the rest of the house. Hang out in your basement when its really hot, and save some money by not cranking up the AC.
My personal fave for 'digging down' is going caving, but that is an extreme example. I had some students once dig a hole at the beach and get into it. It was definitely cooler in there than out on the sand! Basements are always cooler in the summer than the rest of the house. Hang out in your basement when its really hot, and save some money by not cranking up the AC.
Dump Heat
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| Dumping heat on a big cold rock on the AT in Virginia. |
Fuel Your Sweat
Bodies overheat when we don't have enough water to fuel our sweat. We also lose salts and minerals through sweat that are crucial to our bodies functioning properly. The key to hydration is balance. That balance is between water and salt. You've heard of dehydration, but have you heard of hyponatremia? Hyponatremia is the lack of enough salts in the body- and it is tricky because the symptoms tend to be the same or similar to dehydration. Confusing right?!
We need to replace both the water and the salt we lose from sweat. The easiest way to do this is to make sure to eat a snack when drinking large amounts of water, or add an electrolyte mix to the water we're drinking. Your goal is for your urine to be ever so slightly yellow- like a light tinge of yellow. If you have to pee every hour and it's perfectly clear urine, you need some salts!
Put some damn clothes on you hippy! Wait! Hear me out first....
I know what you're thinking. Why would I wear more clothes when I'm already hot? I honestly feel like long sleeves, made from the right kind of fabric, puts my skin in the shade and makes my sweat more efficient at cooling me. This is especially true
in hot dry environments, less so in hot humid environments. Both men and women in Bedouin culture and Arabic culture wear long, loose fitting clothes and it't not simply because of religion. The clothes came first.
The thing is, when you expose skin, you have to protect it with something, and that something is sunscreen. You've got to be religious about reapplying or you will get some level of sunburn and then you'll hate life. Sunscreen may also mess with the rate of evaporation of your sweat, and it definitely won't aid it like wicking fabrics do. There aren't many studies on this. Some people claim it even clogs the holes in your skin that sweat comes out of. (Maybe we should try sunscreen in our armpits, just a thought.) Your sweat evaporating is what keeps you cool, not sweating itself. This is why you hear all those jerks saying 'yeah, but isn't it a dry heat?' Humidity reduces the evaporation rate of your sweat which makes it feel hotter than it is. So 110F in Arizona is more comfortable than 110F in Florida. If I'm going to be in the sun all day, I would rather wear a long sleeve shirt than sunscreen. Ok, I'm rambling. Back to clothes.
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| Mulv Jones wearing traditional Moroccan clothes during a camel trek in the Sahara. |
The thing is, when you expose skin, you have to protect it with something, and that something is sunscreen. You've got to be religious about reapplying or you will get some level of sunburn and then you'll hate life. Sunscreen may also mess with the rate of evaporation of your sweat, and it definitely won't aid it like wicking fabrics do. There aren't many studies on this. Some people claim it even clogs the holes in your skin that sweat comes out of. (Maybe we should try sunscreen in our armpits, just a thought.) Your sweat evaporating is what keeps you cool, not sweating itself. This is why you hear all those jerks saying 'yeah, but isn't it a dry heat?' Humidity reduces the evaporation rate of your sweat which makes it feel hotter than it is. So 110F in Arizona is more comfortable than 110F in Florida. If I'm going to be in the sun all day, I would rather wear a long sleeve shirt than sunscreen. Ok, I'm rambling. Back to clothes.
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| Long sleeves and big dorky hats protect us from the sun |
Here is some basic info on fabrics you'll likely wear, assuming that each garment is composed of 100% of that material. We'll get to blends later. The 'after chill effect' refers to that feeling you get when you have been active and sweating, you stop, and all of a sudden you feel chilled. Hydrophilic (water loving) fabrics tend to do this. This happens in reverse in the summer. If your shirt is soaking wet and there is no breeze or high humidity, you can overheat!
Weave is important! Weave describes how the threads make up the fabric. There are two main kinds you'll run into, flat woven and knit.
- Flat Woven- generally good sun protection if the weave is tight. Tight weaves block out UV but also more wind, so it may hinder evaporation. The best garments have a weave that is tight enough to block out a decent amount of UV and open enough to let wind though.
- Knit- knit fabric has mechanical stretch, meaning the way the fabric is made allows it to stretch. You can take a fiber that is not stretchy and knit it, and the garment will stretch. Generally I avoid knits when I'll be in the sun for a long time because they don't have the UV blocking power of a flat woven. The type of knit and the size of the yarn/thread determines the loft (thickness) of the fabric. The more loft a fabric has, the better it insulates- meaning it is warmer. A sweater has lots of loft while pantyhose have almost none. Knit also has lots and lots of holes. This makes it great for wind to get to your skin, but it does not block out UV as effectively. A white cotton t-shirt has about a UPF of 7. This means that 1 out of 7 of the sun's rays will get through your shirt. Compare that to UPF 50 of a polyester fishing shirt.
On to material types:
- Cotton- This fabric is generally slow to dry unless you're in Arizona with a breeze. It gets very heavy when it is wet and has a relatively long after chill effect depending on how wet the fabric is. Cotton is best in extremely dry environments.
- Polyester- Dries quickly, especially open knits and thin flat wovens. Polyester is hydrophobic- meaning that it does not like to absorb water so it does not get as heavy as cotton when wet. Polyester has a much shorter 'after chill' effect, which can be good or bad depending on the environment. Most polyester garments for hot temperatures have a hydrophilic treating on the inside. This effectively pulls the sweat off of your skin and into the fabric and the hydrophobic polyester pushes the moisture out into the environment.
- Nylon- Nylon is very hydrophobic. It hardly absorbs any water at all which makes it dry extremely quickly. Flat woven nylon can stick to sweaty skin so 100% flat woven nylon clothes should be loosely fitted.
- Lycra / Spandex- The tendency for this fabric to be body hugging lends itself to trapping body heat. It is extremely hydrophillic and stays wet a long time (forever if you live in North Carolina without an electric dryer) The fastest way to dry this material (swimsuits) in a humid pace is to put them in direct sunlight for an hour or two. Unfortunately the UV rays break down the material extremely quickly and cause fading.
- Linen- flat woven linen's open weave lets air through to help sweat evaporate and the stiff nature of flat woven linen keeps it from sticking to the skin. Linen absorbs 20% of its weight in moisture before it feels wet, and it dries quickly, which helps you feel cooler and drier.
Blends- Get the best of everything
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| George wearing a 100% polyester flat woven fishing shirt by Columbia and 90% nylon /10% spandex quick drying zip off pants on a sea kayaking trip |
Some of my absolute favorite pieces of clothing are blends. I have pants that are around 92% nylon and 8% spandex. The high nylon content makes them lightweight and dry lightning fast, and the 8% spandex makes them comfortable to wear without the negatives of spandex. Don't go over 10% spandex or you'll loose the quick dry capability.
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| Me in 93% nylon /7% spandex shorts and a knit polyester shirt in Thailand in the summer |
I tend to wear more flat wovens with some Lycra / spandex in them because I feel like they're cooler and dry faster. I do have some great polyester knits from Patagonia that are also very light and dry quickly, but they don't have the same level of sun protection.
I hope this post will help you stay a little cooler this summer!