The data represent hourly temperatures recorded at four permanent subtidal monitoring sites around San Nicolas Island, CA between November 2015 and October 2019. The temperatures were recorded by TidbiT (registered trademark) v2 model UTBI-001 (Onset Computer Corporation, Bourne, Massachusetts) archival temperature loggers attached at the sea floor. The loggers were deployed approximately 10-12 m deep at Nav Fac (12 m) on the north side of the island, at West End Urchin (11 m) on the southwest side, at east Dutch Harbor (11 m) on the south side, and at Daytona Beach (10 m) near the east end of the island.