35°C in the shade, your t-shirt sticking to your back as early as 9 a.m., and that feeling of being trapped inside your own clothes, of feeling sticky and smelling bad. We’ve all been there. And with every heatwave, our instinct is often the wrong one: we put on the material that looks the thinnest, without asking how it actually reacts to heat and sweat.
Because the truth is that light clothing isn't necessarily cool clothing. A thin cotton jersey can be just as suffocating as a sweater, while a slightly denser but well-designed material can keep you dry all day long. Here, we explain exactly what makes a material breathable (or not), we rank the coolest fibers based on actual textile studies, and we tell you which ones to absolutely avoid if you sweat easily.
If you don't feel like reading it all:
🌬️ A cool material combines breathability, moisture management, thermoregulation, light weave, loose fit, and appropriate color.
🔬 Breathability is what allows air to circulate and heat to escape, a phenomenon that is scientifically measurable (ISO 11092 standard).
🏆 The ranking of the coolest materials: linen, hemp, TENCEL™, light cotton, fine merino wool, silk, and viscose.
👕 How to dress well in high heat: natural material + airy weave + loose fit, with color as a supporting factor.
💧 If you sweat a lot: loose fits and fast-drying fibers (linen, TENCEL™) limit that damp feeling and odors.
🚫 Avoid: polyester, acrylic, and coated fabrics, which trap heat and moisture instead of wicking them away.
Contents
- What properties should you look for when it's hot?
- The importance of breathability in choosing materials
- What is the most breathable material? The ranking
- What clothing material should you wear when it's hot?
- What clothes to wear when you sweat a lot?
- Which materials make you sweat?
What fabric properties should you look for when it's hot?
Before talking about fibers, you need to know what you’re really looking for. A material suitable for heat checks several boxes at once:
- Breathability: its capacity to let air pass through the fabric.
- Moisture management: does the fiber absorb sweat or repel it? And how fast does it dry?
- Thermoregulation: the ability of a fiber to help the body maintain a stable temperature, rather than trapping heat.
- The lightness of the weave, not just the fiber: the same cotton can be cool or stifling depending on whether it is woven into an airy poplin or a dense jersey.
- Color: light reflects heat; dark absorbs it.
- Fit: loose, allowing a volume of air to circulate against the skin.
Material is the foundation, but it is the combination of fiber + weave + fit + color that determines whether you have a comfortable heatwave or a day spent peeling your t-shirt off your back every ten minutes. We detail each of these levers below.
The importance of breathability in choosing materials
Breathability is the number one criterion, and it is also the most misunderstood. A breathable fabric allows air to circulate between the skin and the garment. This airflow has a very concrete role: it continuously wicks away the heat your body releases, and it accelerates the evaporation of sweat on the skin's surface, which creates an immediate cooling sensation. This is a physical principle, not a matter of style.
Conversely, a fabric with low breathability creates a "film" effect: air no longer circulates, moisture stagnates against the skin, and heat accumulates instead of dissipating. This is exactly what happens with many synthetic materials, whose solid fiber structure prevents air from passing through, unlike natural fibers such as linen.
This phenomenon is even scientifically measurable: the ISO 11092 standard, used by textile laboratories, evaluates the thermal resistance and water vapor resistance of a fabric under conditions close to real-life sweating (International Organization for Standardization, 2014). The lower this resistance, the more the fabric lets heat and moisture pass through, and therefore the more breathable it is.
What is the most breathable material? The ranking
Here are the coolest materials for high heat, ranked from most effective to those that require more attention, with studies that support these properties.
1. Linen
Its hollow fiber promotes air circulation and its structure absorbs moisture quickly before releasing it just as fast. A study conducted by the CETELOR laboratory (University of Lorraine) for the Alliance for European Flax-Linen & Hemp compared linen to cotton, viscose, and polyester regarding ventilation, water vapor permeability, and thermoregulation: linen came out on top for ventilation and sweat diffusion (Alliance for European Flax-Linen & Hemp, 2014). Note of caution: it wrinkles easily, which is also its signature.
2. Hemp
Same botanical family as linen, with an equally airy fiber structure and good moisture diffusion. Hemp has one extra feature: it gets softer with every wash, unlike other fibers that degrade over time.
3. TENCEL™ (Lyocell)
A cellulosic fiber derived from eucalyptus wood, recognized for its moisture management. A study published in the scientific journal Fibers and Polymers analyzed the moisture-related comfort properties of several types of lyocell in jersey fabric, confirming their good ability to absorb and diffuse water vapor (Kucukali-Ozturk, 2023). Specifically, TENCEL™ limits the sensation of damp fabric better than conventional cotton, while remaining soft and light. However, it requires more delicate care.
4. Light cotton (poplin, voile)
A hydrophilic fiber that absorbs sweat well, with a soft and familiar feel against the skin. In an airy version (poplin, cotton voile), it remains quite breathable and effective against heat. In a thick version (heavy jersey, fleece), however, it becomes a trap for heat and moisture: it dries slower than linen or TENCEL™, which prolongs the feeling of dampness against the skin.
5. Fine merino wool
Counter-intuitive, but a very fine merino holds its place in this ranking. According to data published by The Woolmark Company, wool fiber can absorb up to twice as much water vapor as cotton and thirty times more than polyester, which keeps the skin drier and limits the growth of odor-causing bacteria (The Woolmark Company, 2021). It must, however, be fine and unlined for summer use, and some skin types tolerate it poorly.
6. Silk
It reflects light (therefore heats up less) and dissipates heat through radiation, all while absorbing sweat and drying quickly. Trade-off: it can yellow at the armpits and requires demanding maintenance.
7. Viscose
Fluid drape and a "cold" feel on contact, pleasant in loose pieces. However, it shows moisture if the fabric is too thin or the cut too tight.
The common thread of these seven materials: they are natural or cellulosic fibers capable of absorbing moisture and then releasing it quickly, unlike synthetic fibers that repel or trap it, as we see below.
What clothing material should you wear when it's hot?
Linen and TENCEL™, seen above, remain the safest bets for summer or a heatwave, whether in a t-shirt or a light shirt. Light cotton (poplin, voile, gauze) is very suitable for everyday use or the office, as long as the weave remains airy. But the material alone is not enough: three other factors make the difference once the fiber is chosen.
- Weight and weave: below about 180 g/m² and with an open weave, air passes significantly better, regardless of the fiber.
- Fit: prioritize loose t-shirts, flowing shirts, wide trousers, and avoid anything that constricts. It is the volume of air between the fabric and the skin that does the cooling work, not just the material.
- Color: useful to know if you are staying in the sun for several hours. Note also that the density of the weave plays a greater role in UV protection than the nature of the fiber itself.
The simple rule to remember: the more the material in direct contact with the skin is natural, breathable, and well-cut, the better your body handles the heat.
What clothes to wear when you sweat a lot?
If you sweat easily, the cut matters almost as much as the fiber:
- Comfortable armholes and an open back, so that air circulates at the most sensitive contact points (back, chest, crook of the elbow).
- Fast-drying fibers: linen first, followed by TENCEL™, which has the advantage of being specifically more effective than standard cotton at limiting the damp feeling.
- Fibers that manage bacteria and odors well, such as TENCEL™ or fine merino wool (see the ranking above).
- Light colors for heat, but keep in mind that they can make sweat marks more visible depending on the fabric: a print or a light texture often hides better than a very light solid color.
For the night, if you tend to sweat while sleeping, the same principles apply to bedding: cotton, linen, percale, or jersey rather than synthetic materials or overly dense blends.
Which materials make you sweat?
Conversely, some materials should be avoided as soon as the thermometer climbs, not because they are "bad," but because their structure works in opposition to what we are looking for in hot weather:
- Polyester and polyamide (nylon): hydrophobic fibers, which repel water instead of absorbing it. Sweat remains trapped against the skin or pushed toward the outside of the garment, creating that sticky "film" effect. In the long run, these fibers also retain more of the bacteria responsible for bad odors.
- Acrylic: an inherently insulating fiber that warms instead of regulating and does not manage moisture.
- Coated or synthetic satin fabrics: visually attractive, but their surface retains heat and shows marks quickly as soon as the air becomes heavy.
The real issue is therefore not just "natural vs. synthetic," but the actual ability of a material to absorb moisture and then release it quickly, exactly the properties we measured and ranked above.
Conclusion
The winning trio against the heat: linen, TENCEL™, and well-woven light cotton, combined with a loose fit and appropriate color. Conversely, polyester, acrylic, and coated fabrics should be avoided as soon as the mercury rises, regardless of the base fiber.
At Lucid, this is exactly the logic that guides our choice of materials: recycled cotton combined with TENCEL™ Lyocell for our t-shirts, certified European linen for our shirts, shorts, and light trousers, or even recycled wool for our warmer pieces. Always with the same idea in mind: garments designed to be worn comfortably, for a long time, without sacrificing either comfort or the planet. If this approach speaks to you, take a look at our t-shirt collection; you will surely find something to get through the summer (and the heatwaves) without sweating buckets.
Sources:
Alliance for European Flax-Linen & Hemp. (2014). Flax-Linen comfort and performance study. CETELOR, Université de Lorraine. https://allianceflaxlinenhemp.eu/en/flax-performance-and-properties
International Organization for Standardization. (2014). ISO 11092:2014 — Textiles — Physiological effects — Measurement of thermal and water-vapour resistance under steady-state conditions (sweating guarded-hotplate test). ISO. https://www.iso.org/standard/65962.html
Kucukali-Ozturk, M. (2023). Comparative analysis of different lyocell types: Structural, physical, mechanical, and moisture-related comfort properties in single jersey fabrics. Fibers and Polymers, 24, 4429–4439. https://doi.org/10.1007/s12221-023-00382-7
Chekushine, A. (2026, January 18). Which material to choose for summer when it's very hot: the guide to staying cool. Misciano. https://misciano.com/blogs/journal/quelle-matiere-choisir-pour-lete-quand-il-fait-tres-chaud-le-guide-pour-rester-fraiche-sans-compromis
The Woolmark Company. (2021). Wool is naturally odour resistant. Woolmark. https://www.woolmark.com/industry/research/wool-odour-resistant/
