Outdoor Recreation

When Cotton Doesn’t Kill: Ideal Hot Weather Fabrics

In 1935, two outdoors people living in Seattle confronted a problem. They loved to mountaineer, but a good Austrian ice axe would break the bank. So to solve the problem, they cut out the middlemen and started ordering the ice axes directly from Austria, saving a whole lot of money in the process. Their strategy worked so well that soon their friends got into it, first buying only ice axes but gradually diversifying into other mountaineering gear as well. The enterprise grew and grew, first taking up just a shelf, then a whole building, then a whole bunch of buildings, and then becoming the multi-million dollar retail chain we all know and love (1).

The name of this chain? REI.

The ice axe that started it all (1).

What is the purpose of this story?

To illustrate that mainstream outdoor recreation in the United States has its roots in the Mountain West. If you are still not convinced, go ahead and read about the origins of other popular outdoor brands, such as The North Face, Columbia Sportswear, or Black Diamond. Or read about the origins of outdoor recreation groups like the Sierra Club (hint, the name). The only exception that immediately jumps to mind is Patagonia, whose founders decided to name their company after a mountainous region of South America, rather than North America.

The origins of mainstream outdoor recreation in the United States has a number of profound implications, but here I am going to focus on what it means in the context of specialized outdoor clothing. If you have ever been to the mountains, I am sure you know that, thanks to elevation and orographic lift (2), mountains tend to be colder and wetter than low-lying areas. As a result, outdoor clothing and the wisdom surrounding it is designed to keep you warm and dry in the cold, wet conditions generally present in the mountains. 

A typical day in the mountains.

Keeping warm and dry in the mountains generally means wearing fabrics that dry quickly and/or insulate well when damp, such as polyester, nylon, and wool. Wearing these fabrics serves to get rid of body moisture and keep your skin as warm and dry as possible (3, 4)

Alternatively, fabrics made from plants, like cotton, linen, and hemp, behave just the opposite. Plant fabrics contain lots of cellulose, a molecule that loves water, causing clothing made from these materials to absorb more water and take longer to dry than fabrics from other sources (5). These fabrics’ love for water is more than just uncomfortable. Wet cotton, for example, saps heat from the body so effectively that it can put the wearer at serious risk of hypothermia in cold weather, an idea that is described by the ubiquitous phrase in the outdoor community: “cotton kills” (6, 7)

While this phrase is certainly true, its nuance has been lost. Now, outdoor brands avoid plant fabrics for virtually all of their technical clothing, not just the ones made for cold weather (8, 9). And doing so is a great disservice to the outdoor community, as plant fabrics have a number of desirable qualities for hot weather.

I was crazy enough to spend 30 hours per week outdoors guiding during the hottest summer in Texas history (10, 11). I started the summer wearing my fancy, ultra-cooling, UV-shielding polyester shirt, expecting it to keep me as comfortable as anyone could be in triple-digit temperatures. But I quickly found that I overheated faster than my customers who wore regular cotton t-shirts, and that as soon as I changed into cotton, I felt a lot more comfortable.

But why?

Polyester is actually less breathable than cotton. Breathability refers to how easy it is for water vapor to pass through a fabric, and water vapor passes through moisture-loving cotton far more easily than it passes through moisture-hating polyester. As a result, wearing polyester made it difficult for the vapor from my evaporating sweat to escape, causing the air next to my skin to feel even stickier than the ambient air (12). My nylon shirts also had similar properties (13). Wool, while breathable, was simply too good at retaining heat to wear on a hot day (14).

Alternatively, the cotton soaked up my sweat and, damp from it, sucked the warmth right from my body. While it was certainly true that the cotton took longer to dry, this hardly mattered when it was so hot that even a glass of water could evaporate by the end of the day! Cotton, far from killing me, saved me from the unrelenting heat. And as I later learned, cotton is just the tip of the iceberg.

Linen, a fiber made from flax, has long been regarded as the best fabric for the heat in tropical areas across the world (15, 16). This is partly because linen has a high rate of thermal conductivity, meaning that even when dry it can quickly transfer heat away from the body (17). And if it does get wet, linen dries more quickly than cotton, making it a bit more comfortable when you are especially sweaty. Linen is also very stiff, keeping it from clinging to the skin and instead causing it to act more like a wearable shade canopy than clothing. In addition, linen is one of the strongest known plant fibers, allowing linen products to be thin yet durable (18).

A field of flax plants that will soon be turned to linen.

Hemp, another up-and-coming plant fabric, seems to have similar properties as linen. Fabric made from hemp is also anti-microbial, meaning that you can wear it for longer before it starts to smell (19)

In addition to being great hot weather fabrics, hemp and linen used to be among the world’s most popular fabrics. Linen was the most popular fabric in Europe and its American colonies until it was overtaken by cotton in the 1800’s, when slavery and industrial processing methods made cotton cheaper to produce, yet much less ethical (20). Hemp fell out of popularity in the early 1900’s, when it was caught in the crossfire of the United States government’s criminalization of marijuana. Before being criminalized, hemp used to be so ubiquitous that even George Washington farmed it (21)!

Wearing linen pants and a hemp shirt on a 100+ degree day.

It is worth noting that I have omitted one important fact: that the qualities of fabrics are impacted by more than just the types of fibers that constitute them. Polyester, for example, can be made more breathable depending on how the fibers are woven together and if special coatings are used. And there are a number of very breathable (albeit expensive) polyester clothes on the market (2224). Still, clothes made from linen, hemp, and even cotton, on average, are much cooler and more breathable than clothes made from polyester, nylon, or wool.

A shift toward linen and hemp clothing would also do a lot of good for the world. Unlike cotton, they are not intertwined with a dark history of oppression and environmental destruction and require significantly less water and fertilizer to produce (2527). And unlike synthetic fabrics like nylon and polyester, which are made from plastic, plant fabrics are generally biodegradable and do not leach microplastics into the environment (28, 29)

A greater use of these fabrics would also make us more comfortable in the outdoors. Since all fabrics have their own unique strengths and weaknesses, there is no universal “best fabric”. We need different things from our clothing under different conditions, and wearing pure polyester on a hot, humid day makes about as much sense as wearing cotton in the snow. And the outdoor community is starting to recognize this fact. Some outdoor brands are moving away from the rigid dogma of “cotton kills” and have even mentioned cotton in their warm weather clothing guides. Mentions of linen and hemp, however, are still lacking (30, 31).

Despite failing to include linen and hemp in their clothing guides, some brands have begun to sell clothing containing varying degrees of these fabrics. They still seem to be regarded as novelties and fashion items rather than things to be worn for strenuous activity, but it does seem that change is in the air. Hopefully before long the outdoor community will realize that wearing plant fabrics in the heat will keep us a whole lot more comfortable outdoors.

Have any questions or feedback? Contact me.



  1. REI History: It Started With An Ice Axe. Uncommon Path – An REI Co-op Publication (2016), (available at https://www.rei.com/blog/camp/rei-history-it-started-with-an-ice-axe).
  2. R. A. Houze Jr, Orographic effects on precipitating clouds. Rev. Geophys. 50 (2012), doi:10.1029/2011rg000365.
  3. H. B. Rochfort, Material Science: The Art of Layering. Uncommon Path – An REI Co-op Publication (2020), (available at https://www.rei.com/blog/snowsports/material-science-layering).
  4. N. Kasturiya, M. S. Subbulakshmi, S. C. Gupta, H. Raj, System design of cold weather protective clothing. Def. Sci. J. 49, 457–464 (1999).
  5. A. Célino, S. Fréour, F. Jacquemin, P. Casari, The hygroscopic behavior of plant fibers: a review. Front Chem. 1, 43 (2013).
  6. P. Werner, Why Does Cotton Kill? Section Hiker (2021), (available at https://sectionhiker.com/why-does-cotton-kill/).
  7. How To Dress in Cold Weather. REI, (available at https://www.rei.com/learn/expert-advice/how-to-dress-in-cold-weather.html).
  8. Sun Protection Clothing. Patagonia, (available at https://www.patagonia.com/shop/sun-protection-clothing).
  9. Sun Protection. Outdoor Research, (available at https://www.outdoorresearch.com/us/sun-protection).
  10. R. Villalpando, Austin on pace to make 2022 summer its hottest ever. Austin American Statesman (2022), (available at https://www.statesman.com/story/weather/2022/07/25/austin-temperatures-breaking-records-2022-summer-is-its-hottest-ever/65380360007/).
  11. R. Graham, Living Through Texas’ Hottest Summer. The New York Times (2022), (available at https://www.nytimes.com/interactive/2022/07/15/us/texas-heat.html).
  12. K. C. Schuster, F. Suchomel, J. Männer, M. Abu-Rous, H. Firgo, Functional and comfort properties of textiles from TENCEL® fibres resulting from the fibres’ water-absorbing nanostructure: A review. Macromol. Symp. 244, 149–165 (2006).
  13. B. Kumar, V. Somkuwar, Textiles for Functional Applications (BoD – Books on Demand, 2021).
  14. D. Bosia, L. Savio, F. Thiebat, A. Patrucco, S. Fantucci, G. Piccablotto, D. Marino, Sheep Wool for Sustainable Architecture. Energy Procedia. 78, 315–320 (2015).
  15. A. E. Korlu, E. G. Bozaci, Properties of Flax and Retting of Flax. Tekstil ve Konfeksiyon. 16, 276–280 (2006).
  16. Karunaratne, Withanage, Consumer demand for linen apparel fashion in Sri Lanka. World Sci. News (available at https://yadda.icm.edu.pl/yadda/element/bwmeta1.element.psjd-08a5393c-9fe0-4ceb-acbf-6802a8b21cc4).
  17. I. Cartagenas, How Thermal Conductivity Decides What You Put in Your Closet. Thermtest Instraments (2016), (available at https://thermtest.com/how-thermal-conductivity-decides-what-you-put-in-your-closet).
  18. 15 natural fibres. FAO (2009), (available at https://www.fao.org/natural-fibres-2009/about/15-natural-fibres/en/).
  19. S. I. Editor, Advances in the performance and application of hemp fiber. Int. J. Simul. Syst. Sci. Technol. (1970), doi:10.5013/ijssst.a.17.09.18.
  20. P. M. Solar, The triumph of cotton in Europe. London School of Economics (2012), (available at https://cgeh.nl/sites/default/files/Solar%20Triumph%20Cotton.pdf).
  21. R. Deitch, Hemp: American History Revisited: The Plant with a Divided History (Algora Publishing, 2003).
  22. W.-C. Tsen, Y.-C. Shu, K. Hsiao, Preparation and Physical Properties of Hollow Polyester Filaments with High Breathability, Water Absorption and Release Rates. Polym. Polym. Compos. 14, 107–118 (2006).
  23. M. B. Sampath, M. Senthilkumar, Effect of Moisture Management Finish on Comfort Characteristics of Microdenier Polyester Knitted Fabrics. J. Ind. Text. 39, 163–173 (2009).
  24. S. Pongsathit, S.-Y. Chen, S.-P. Rwei, C. Pattamaprom, Eco‐friendly high‐performance coating for polyester fabric. J. Appl. Polym. Sci. 136, 48002 (2019).
  25. M. Nigam, V. Yadav, Linen-the classic fibre for futuristic fashion, (available at http://scientificresearchjournal.com/wp-content/uploads/2019/04/Social-Science-6_A-659-667-Full-Paper.pdf).
  26. A. G. Duque Schumacher, S. Pequito, J. Pazour, Industrial hemp fiber: A sustainable and economical alternative to cotton. J. Clean. Prod. 268, 122180 (2020).
  27. A. L. Olmstead, P. W. Rhode, Cotton, slavery, and the new history of capitalism. Explor. Econ. Hist. 67, 1–17 (2018).
  28. A. Šaravanja, T. Pušić, T. Dekanić, Microplastics in Wastewater by Washing Polyester Fabrics. Materials . 15 (2022), doi:10.3390/ma15072683.
  29. A. Shrivastava, S. Dondapati, Biodegradable composites based on biopolymers and natural bast fibres: A review. Materials Today: Proceedings. 46, 1420–1428 (2021).
  30. T. Schimelpfenig, Y. Zein-Phillipson, Hot-Weather Hiking Tips. REI, (available at https://www.rei.com/learn/expert-advice/hot-weather-hiking.html).
  31. H. Oliver, How to Hike And Backpack In the Heat. Outdoor Research (2020), (available at https://www.outdoorresearch.com/blog/how-to-hike-and-backpack-in-the-heat).

1 thought on “When Cotton Doesn’t Kill: Ideal Hot Weather Fabrics”

Leave a Reply

Your email address will not be published. Required fields are marked *