Local‐scale microclimatic conditions in forest understoreys play a key role in shapingthe composition, diversity and function of these ecosystems. Consequently, under-standing what drives variation in forest microclimate is critical to forecasting ecosys-tem responses to global change, particularly in the tropics where many speciesalready operate close to their thermal limits and rapid land‐use transformation isprofoundly altering local environments. Yet our ability to characterize forest micro-climate at ecologically meaningful scales remains limited, as understorey conditionscannot be directly measured from outside the canopy. To address this challenge, weestablished a network of microclimate sensors across a land‐use intensity gradientspanning from old‐growth forests to oil‐palm plantations in Borneo. We then com-bined these observations with high‐resolution airborne laser scanning data to char-acterize how topography and canopy structure shape variation in microclimate bothlocally and across the landscape. In the processes, we generated high‐resolutionmicroclimate surfaces spanning over 350 km2, which we used to explore the poten-tial impacts of habitat degradation on forest regeneration under both current andfuture climate scenarios. We found that topography and vegetation structure werestrong predictors of local microclimate, with elevation and terrain curvature primarilyconstraining daily mean temperatures and vapour pressure deficit (VPD), whereascanopy height had a clear dampening effect on microclimate extremes. This buffer-ing effect was particularly pronounced on wind‐exposed slopes but tended to satu-rate once canopy height exceeded 20 m—suggesting that despite intensive logging,secondary forests remain largely thermally buffered. Nonetheless, at a landscape‐scale microclimate was highly heterogeneous, with maximum daily temperaturesranging between 24.2 and 37.2°C and VPD spanning two orders of magnitude.Based on this, we estimate that by the end of the century forest regeneration couldbe hampered in degraded secondary forests that characterize much of Borneo's low-lands if temperatures continue to rise following projected trends.