The unstructured jacket is a perfect solution to summer time heat when a formal appearance is still needed. What to look for: unlined, or partial lining; no padding; fabric should be cottons, linens, or tropical wool. Tailoring is particularly important to get the look just right, as the jacket will drape from the shoulders. The inevitable wrinkles can be easily steamed out at the end of the day.
A Brunello Cucinelli jacket featured in a recent T Magazine piece.
Examples from Men’s Ex.