When it rains most people add rainwear over clothes which are already warm enough or too warm. That extra layer causes overheating and sweat soaked clothes, and they blame the rainwear instead of excess clothing layers for overheating.
That was the main reason for the development of Gore-Tex and the millions spent promoting it for what it isn't. Smart people avoid getting hot by wearing less clothes under their rainwear.
If you've never tried modern rainwear, you're in for a pleasant surprise. Every year waterproof clothing gets better, lighter, tougher, cheaper and more breathable.
From the Greek hydros (water) and philos (friend), hydrophilic describes water loving tendencies. The opposite is hydrophobic fabric, which absorbs little or now water.
There is no need for a microscope to determine whether or not a material is designed with hydrophilic properties. A simple test consists of gently placing a drop of water on the surface of a cloth.
The quicker the water drop spreads over the fabric, the more hydrophilic the material. A drop of water that stays on the surface without wetting the fabric indicates no hydrophilic characteristics whatsoever. In fact this behavior is, in some cases, desirable.
For impermeable fabrics, a finish applied on the fabric prevents water or oil penetration. Textile engineers can select the level of repellency by adjusting the surface tension. Allowing a low surface tension makes it easier for the liquid to diffuse through a larger surface area resulting in quick evaporation, thus a higher comfort sensation.
For underwear applications, the fabric must be hydrophilic to move away moisture for the skin interface and spread the limit on the largest possible area to favor evaporation. Often to help this phenomenon, a "brushed" fabric is used causing a considerable increase in surface area thus enhancing the comfort level.
Polyester fabric is good to wear in hot weather because it helps you to prevent sweat quicker and faster.
Showerproof fabric is natural and breathable with no extra coating. It has natural water repelling properties sufficient for most light showers. The seams are not taped, which almost halves the labour costs so will make the item cheaper. Water will seep through the seams and the fabric in heavy rain.
Water resistant clothes will soak through after a while. If your clothes feature a water-resistant fabric, it usually means that a coating has been applied to the material to help repel water. This works well for light rain and drizzle, but won't handle steady rain.
For most water sports a breathable water resistant windproof fabric is best, as you'll get wet anyway you occasionally when you jump into the water. You only need the windproofing and sun protection.
If you're looking for real protection, get true waterproof fabric.
To be waterproof, rain gear must be made of waterproof fabrics and have sealed or taped seams
so that rain cannot leak through the small perforations made by sewing needles during construction.
Sealing and taping seams takes special equipment and extra time, adding to the garment's cost.
Strength is given by a number. 210 is the thread count vs. 210 denier. The 210T fabric is woven, but the 210D fabric is knitted.
In both cases the number is a measure of the density of the material, but for thread count a higher number represents a denser weave (threads per inch) while with a knitted material a higher denier is a sheerer, more delicate knit.
Denier is a weight measure of the yarn. It is used for man made yarns like polyester, nylon etc.
1 Denier is "weight of 9000m of yarn in grams".
So 210D means if you take 9km of that yarn and weigh it, it only weighs 210g.
The yarn can be anything nylon, polyester, whatever.