Seersucker double breasted jacket, $298 by Brooks Brothers

The Lightest Layer

Chambray blazer, $395
by Rag & Bone

Oxford cloth jacket, $485
by APC

The spring and summer is no time to stop wearing a jacket, it's simply time to wear a different jacket. Lightweight, semi-lined and unstructured, these light blue blazers let you dress up a casual warm weather look without sacrificing any comfort. APC cut its classic two-button blazer out of breezy oxford cloth. Rag & Bone also went with an unfussy shirting material. Their cropped jacket is made from a washed chambray with patch pockets and a 3/2 roll lapel. Brooks Brothers offers a sharp twist on the prep's summer standby—a relaxed double breasted seersucker jacket in the brand's more modern Milano fit.

• Phoenix is the hottest US city, averaging 106 days above 99°F annually.