23 of 55 destinations scored for swimming are prime in September — 80 or better on conditions alone. Highest: Hawaiʻi, the Big Island (97), Oʻahu & the North Shore (95), Maui (92). In August 35 are prime; in October, 6.
Every destination scoring 55 or better for swimming in September, highest first. Ties are listed alphabetically.
Most places have one or two months that are genuinely better — and a booking moment that comes a lot earlier than the trip. I’ll write when one of those is coming up. No schedule, no filler.
Somewhere missing from the list? Write to info@pennyswindow.com and I’ll score it.