Abstract

Changes in rock-surface temperature generate thermal stresses and freeze-thaw conditions that can generate rockfalls. Capturing the full range of temperature variation, from seasonal variability to hourly extremes, is important, but data sets recording such characteristics with sufficient temporal and spatial resolution remain scarce, limiting our understanding of temperature-driven rockfall. To address these limitations, we present a year-long data set of cliff surface temperatures collected using infrared thermography at hourly intervals and 0.12 m resolution across a similar to 1,315 m2 rock slope in northeast England. Temperatures ranged from -11.7 degrees C to 40.2 degrees C (a similar to 51.9 degrees C range), with 123 days of freeze-thaw cycling and rapid changes up to +20 degrees C per hour during heating and -13.7 degrees C per hour during cooling. These dynamic thermal conditions contrast sharply with air temperature records, which fail to capture the magnitude and rates of thermal conditions on rock surfaces. When direct solar radiation is low, rock-surface temperature variation is governed mainly by the thermal properties of the rock; when solar radiation is high, cliff morphology, via shadowing, exerts greater influence on rock-surface temperature. Our results highlight the limitations of using air temperature or short-term, low-resolution data to characterize rock slope thermal regimes. Our analysis provides new field insight into thermal conditions that promote subcritical crack growth and rockfalls, offering crucial context for interpreting existing laboratory-derived thermal thresholds for rock damage and how they translate to rockfall activity under future climate scenarios.