Percale sheets are sheets made from plain-weave fabric. This means that the threads running across--the weft--and the threads running lengthwise--the warp--weave over and under one another one at a time. This type of weave creates a fabric that is tight, smooth, firm and fine.
Because percale sheets are breathable and medium-weight, they are especially suitable for warm-weather sleeping. These sheets are often cotton and have a thread count of at least 180 per square inch. Sometimes percale is made from a cotton and polyester blend that minimizes wrinkling. Fewer wrinkles appear on 100 percent cotton percale sheets when they are dried on a low temperature setting and are removed from the dryer immediately after the cycle finishes.