Summer shows up in email as warm palettes, sunlit photography, and language built around heat, travel, and time off. Brands lean on it to launch seasonal lines, run end-of-season sales, and shift to a lighter tone. The strongest examples commit to a specific feeling (poolside, road trip, late evening) instead of generic brightness, and pair the mood with one clear offer. Watch for cluttered layouts and washed-out contrast that hurt readability outdoors.