Summers in the American state of Florida are incredibly hot and humid. With temperatures often in the mid 90F/30C range, you must dress appropriately for the searing, sticky heat. With that said, my favorite summer shirts are either lightweight linen or cool chambray.
High quality linen is very expensive. It is grown from the flax plant, which is very temperamental and tricky to grow. The fibres are hand-plucked from the stocks of the flax plant. This is a very tedious task, requiring much time and effort. Originally, linen was reserved only for royalty. Linen of higher qualities will not have the "slubs" or knots/bumps woven in the fabric. The fabric is naturally resistant to dirty, naturally moth-resistant, and wicks water away from the skin. Don't fold linen - hang it up so you don't break the fibres (this also will prevent additional wrinkles).
Chambray is a soft, lightweight fabric for the searing summer as well. The fabric is usually made of cotton, and is formed using a tight, plain weave with 2 colors of yarn - most notably white and blue, resulting in a slight lustre and lightly faded appearance. The fabric originated in Northern France in the town of Cambrai, where they first used the fabric to made sunbonnets.
J. Crew makes a fabulous vintage chambray work shirt. Neiman Marcus stocks beautiful chambray linens. The great Italian designer Roberto Cavalli makes the sexiest chambray pants and skirts for women, but doesn't feature them all too often - so keep an eye out for the prize.
No matter where you live, inclement weather is bound to find come your away. So dress for success. Dress for the weather. And dress well.