To better understand the physiological effects of climate change and ocean acidification on marine organisms, information on the environmental conditions experienced in their natural habitats is required. Data from long-term monitoring studies capture in situ variability of environmental parameters that are used to relate experimental findings with field conditions. Elands Bay on the west coast of South Africa is a key location for such research and monitoring. It is a popular location for West Coast rock lobster fishing and therefore an important sentinel site for a commercial fishery species and the benthic communities upon which it depends. Low pH conditions exist along the west coast due to effects of upwelling, while cold-bottom waters in Elands Bay often result in low oxygen events responsible for mass walkouts of rock lobster. Additional exposure to extreme stressors associated with climate change can exacerbate impacts on their physiological processes. For example, acute thermal stress experienced during a marine heatwave may cause a rapid deterioration of cellular processes and performances beyond tolerance limits, affecting survival, growth and development. In South Africa, occurrences of marine heatwaves are increasing all along the coastline, and occur on average at least once a year. Data on temperature extremes are therefore important to design experiments and calculate thermal windows. We initiated long-term monitoring of inshore environmental parameters in Elands Bay by deploying temperature loggers in representative habitat types: intertidal rock pools varying in surface area, volume and position along the shore, sun-exposed habitats, and subtidal habitats. The subtidal logger is positioned at an overhang in the same vicinity of the rockpools and housed in a mooring block. Here we present the raw temperature data from the subtidal from 5 June to 18 October 2023.