Is cotton or polyester better for hot weather?

Cotton, generally, because it is breathable and absorbs sweat, which feels more comfortable in everyday heat. Polyester does not absorb moisture and can feel clammy, though specially engineered performance polyester wicks sweat for athletic use.

Why are so many clothes a cotton-polyester blend?

Because the two fibers cover each other's weaknesses. Cotton brings softness, breathability, and comfort; polyester brings strength, wrinkle resistance, fast drying, and shape retention. A blend like 65/35 or 50/50 is cheaper and easier to care for than pure cotton while staying more comfortable than pure polyester.

Cotton shrinks, especially in hot washing and drying, unless it has been pre-shrunk. Polyester is dimensionally stable and resists shrinking, which is one reason it is blended into cotton garments.

Side by side

Cotton vs Polyester

Cotton and polyester are the two most common apparel fibers, and they sit on opposite sides of the natural and synthetic divide. Cotton is a natural plant fiber, soft, breathable, and absorbent. Polyester is a synthetic made from PET plastic, strong, quick-drying, and wrinkle-resistant. The two are so complementary that the world's most common everyday cloth is a blend of them.

Cotton

No. 126

the seed-hair fiber, woven into countless cloths · first documented Antiquity

Polyester

No. 122

woven or knitted from PET filament or staple · first documented 1941

The differences

Aspect	Cotton	Polyester
Origin	Natural: the seed hair of the cotton plant.	Synthetic: a polymer spun from petroleum-derived PET.
Breathability	Breathable and absorbent; pulls moisture into the fiber.	Low absorbency; wicks moisture along the surface but can feel clammy.
Drying and wrinkles	Dries slowly and wrinkles.	Dries fast and resists wrinkling; holds a pressed shape.
Durability	Durable but wears and can shrink.	Very durable, abrasion-resistant, and shrink-resistant.
Comfort and feel	Soft and comfortable against the skin; less prone to static and odor.	Smoother but warmer to wear; can hold odor and static.
Environment	Biodegradable, but water- and pesticide-intensive to grow.	Cheap and long-lasting, but petroleum-based and sheds microplastics.

Which to choose

Choose cotton for breathable, soft, natural comfort next to the skin. Choose polyester for durability, fast drying, and wrinkle resistance. For most everyday clothes, a cotton-polyester blend is the deliberate compromise, borrowing cotton's comfort and polyester's easy care.

Common questions

Is cotton or polyester better for hot weather?: Cotton, generally, because it is breathable and absorbs sweat, which feels more comfortable in everyday heat. Polyester does not absorb moisture and can feel clammy, though specially engineered performance polyester wicks sweat for athletic use.
Why are so many clothes a cotton-polyester blend?: Because the two fibers cover each other's weaknesses. Cotton brings softness, breathability, and comfort; polyester brings strength, wrinkle resistance, fast drying, and shape retention. A blend like 65/35 or 50/50 is cheaper and easier to care for than pure cotton while staying more comfortable than pure polyester.
Which shrinks?: Cotton shrinks, especially in hot washing and drying, unless it has been pre-shrunk. Polyester is dimensionally stable and resists shrinking, which is one reason it is blended into cotton garments.

Full entry: Cotton Full entry: Polyester

Sources & References

1.Cotton, Wikipedia
2.Gossypium, Wikipedia
3.Polyester, Wikipedia
4.Polyethylene terephthalate, Wikipedia