Strategies for Backpacking in the Heat: Daily Routine and Gear Considerations

Thanks for the article.

One thing I would add is bring electrolyte tablets or powder to add to water. A few years ago I was on a trip that was unexpectedly hot (expected 70F, was 95F – inland Ventana wilderness is more like Salinas than Big Sur… doh!). At the end of the day my whole body started to cramp. Any movement resulted in pain. couldn’t add pressure to the cramping area because the movement to reach it caused new craps. Thankful, a friend has gifted me some electrolyte tablets which I had thrown into my bag on a lark. I had to fight through the cramping to get them out of my pack. Around 30 minutes later all the cramping stopped.

As to water needs… lifted from my water page

I developed a sense of my water needs by repeatedly running an experiment. I would weighing myself naked, get dressed. engaged in activities at different MET intensities and temperatures (no peeing during the experiment) for 1-4 hours, removing clothing, drying with a towel, and then weighing myself measure weight loss due to sweating / perspiration / breathing. I lost 1L every three hours when it’s 30-60F and I am moderately active (MET 3-6), around 1L for every 1.5-2 hours 60-80F, and 1L every hour when it’s more than 80F.  When >9 METs water lost was 3x my normal rate. When I gave chat-gpt the prompt “what’s the rate of water loss in humans at different MET and temperatures? How does variance of humidity effect this?” I got results compatible with my self experimentation and some added nuance.

And that’s why Bobby slipped away. Just follow the Big Sur river down to the beach and you won’t be hot.

I find what I drink makes a big difference. Mostly cutting out alcohol and sugary drinks. You sweat out your poisons. Having clean sweat is more efficient.

Excellent article, lots of good info here. A couple of adds:

If you are not a fan of electrolyte drinks (I am not), salty snacks and dried fruits will meet your electrolyte needs.

I carry all my water in 1 or 2 liter containers. Two reasons – 1) if you get a leak or seam blow out in a 6L bladder (not likely, but it happens) then you are in trouble. It’s much easier to deal with losing a smaller bladder. 2) Easier to balance out that water weight in your pack with multiple small bladders than one large one.

Regarding taking a break between 12 and 5 – it seems like when it is hot, and the surrounding air is so hot that unless you find a large tree that provides shade, isn’t it better to be moving – even slowly? (Finding such trees in the desert is next to impossible).

Regarding taking a break between 12 and 5 – it seems like when it is hot, and the surrounding air is so hot that unless you find a large tree that provides shade, isn’t it better to be moving – even slowly? (Finding such trees in the desert is next to impossible).

I think it depends. When the air is above the temperature of our core, cooling becomes limited. Bright sun makes it worse, but dry air at least allows sweat to evaporate. Low humidity seems more important than air temperature alone. Wind can make a huge difference, as well.

With the right clothing and weather/climate, walking could be fine. As you say, control your pace as appropriate.

If it is hot and humid with no breeze, then that might be a time to experiment with man-made shade and a siesta. Maybe two layers of space blankets with an air gap in between?

It seems as though somebody, somewhere, must have come up with a pocket size hot-weather Super Shelter by now.

Good topic and informative article. Not only do the majority of my hikes have long water carries in warm to hot weather, I work outside year-round in heat quite a bit more humid than what’s covered here. That said, the commentary and tips offer good advice for hot/humid weather for the most part. I would add that carrying UL electrolytes like salt stick caps is super important, and sun hoodies arent always the best option for hot/humid, because hot/humid usually implies biting insects. I prefer a woven, collared, button up worn in conjunction with a full brim hat and umbrella. Surplus boonie hats can be wet down and worn to cool ya a bit. unfortunately, with increasing humidity and heat during southeastern summers, understanding wet-bulb temperature is crucial to safety. I use the this military guide for planning activity in the heat, specifically, pg 6 – https://home.army.mil/wood/application/files/8416/2765/1794/Heat_Illness_Pocket_Guide.pdf

This is also a good source for understanding safe activity levels in high heat conditions – https://ph.health.mil/PHC%20Resource%20Library/cphe-heat-ehip-guide.pdf

Because you lose other electrolytes… if you take just salt it will produce a larger imbalance which can actually worsen dehydration.

I took “salt” to mean all electrolytes.  If they mean sodium only, ok.  After a lit survey, recommendation was Salt stick Caps (50 min mark):

Taking too much water without electrolytes can cause hyponatremia

My feet and hands swell when I hike hard in high heat and hydrate regularly, these salt stick caps avoid it.

My Renal Physiology Professor was quite adamant and correct , it’s almost impossible for a normal, healthy human to run out of sodium/electrolytes even if severely sweating. Kidneys are clever and do their job well. Vomiting, diarrhoea etc is a different story. Most ‘sport electrolyte’ drinks are marketing, not medically needed.

But running out of water is easy, like nutrition expert Dr Michael Mosely on a short walk on a hot Greek island, no shade and reflected heat from rocks. In Central Australia, the National Parks rangers close the walks when the anticipated temperature is over 36 C (97F) because there have been too many deaths of tourists. This week in Alice Springs it was 43 C (110F), at the start of summer.

An easy 5km walk like the Valley of the Winds (https://uluru.gov.au/things-do/activities/walks/kata-tjuta-walks/valley-winds-walks/) which I did with kids 3, 8, and 13 had killed 2 German tourists a few months earlier. I was asking the ranger why they were closing at a common (not very hot for the Northern Territory) temperature of 36C, and she explained that after these last 2 deaths (they had one small waterbottle each, I carried over 4 litres) the National Parks Service had to close walks for safety.

Prehydrate (drink up before starting), continuously hydrate while walking (a bladder with a tube near my mouth reminds me better than a bottle on the back), and take a big swig every rest stop. At least a litre per hour for walking over 35C, and I’ll always carry extra. That burden of an extra bottle vanishes when you find the ‘permanent’ creek on the map is dry.

The vid I posted reviews studies of sodium loss and efficacy of different electrolytes