Weathering is a foundational process in most Earth systems, but there has been a lack of data directly quantifying what influences mechanical weathering. Here we use multiple years of in situ field data, “listening” to acoustic emissions of naturally cracking rocks, to test a hypothesized link between climate and subcritical crack-tip processes (i.e., the bond-breaking mechanism thought to embody most mechanical weathering). Our results challenge the assumption of a singular dependence of mechanical weathering on stresses. We find that mechanical weathering rates exponentially increase as functions of atmospheric vapor pressure (VP), temperature, and relative humidity, even when controlling for stress-loading. VP exerts the most pronounced influence on the observed mechanical weathering rates. Put in the context of global climate change, our results underscore the potential for climate-dependent subcritical crack-tip processes to influence all weathering-allied problems including the long-term stabilization of the climate by weathering-carbon-cycle feedbacks.