The trick to spring-summer dressing is pretty much the opposite of fall-winter: the less layers, the better.
And one way to remove a layer while still pulling off a tailored look is to opt for an unlined blazer—preferably in the airiest weave you can find.
The giveaway of a good unlined blazer is the taped seams (our bearded friend here is doing a good job of demonstrating this, by showing the neon-taped interior of his blazer). Most blazers don’t have finished seams because they’ll never see the light of day once the lining has been sewn in. It’s a neat trick—the taped seams—but mostly a good sign of what you should be looking for in a lightweight blazer.