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Rock temperature data collected at one-minute intervals from both the horizontal surface and the four cardinal directions of a rock outcrop show the influence of record interval and aspect on the thermal regime of bedrock as it applies to cryogenic weathering. High frequency data are necessary to identify components of thermal stress fatigue and thermal shock events that play a significant role in rock breakdown. The northern aspect exhibits the lowest temperatures despite its apparent preferential orientation. At the 2 cm depth, temperatures on the northern and horizontal surfaces sometimes stayed above those for the rock surface despite the daytime energy input from solar radiation. Short-term wind fluctuations are considered as a possible explanation. Because the rock temperatures are quite different from those of the air the latter can, in no way, be used as a surrogate for rock thermal conditions. The argument is made that one-minute record intervals are required for thermal data if use is to be made of this information to help explain and understand the weathering regime. (C) 1998 John Wiley & Sons, Ltd.