Temperature and humidity recordings taken inside and outside granitic caverns at a coastal and an inland site in South Australia show that cavern microclimates are characterized by smaller diurnal fluctuations in air temperature, rock temperature and air humidity than occur outside caverns, a result of lower maximum values and/or higher minimum values in caverns. The influence of cavem aspect and size (within the range available) on microclimatic variables was minor. Diurnal fluctuations in air temperature, rock temperature and air humidity were all greater at the inland site than the coastal site. Some implications of these results for rock weathering and preservation of rock art are put forward.