The time‐averaged shear‐wave velocity in the upper 30 m depth from the ground surface, or , is often used as a predictor to describe local site effects in ground‐motion models. Although is typically determined from in situ measurements, it is not always feasible to obtain such measurements due to project restrictions or site accessibility. This motivates the development and use of proxy‐based predictions that leverage more readily available secondary information such as surface geology, topographic slope, or geomorphic terrain classes to estimate the mean and associated uncertainty. Traditionally, empirical distributions of have been observed to have long right tails, leading to high levels of associated uncertainty. In this study, we present a physical framework that is grounded in fundamental principles of geostatistics and probability to explain the uncertainty and skewness associated with measurements. Specifically, by invoking Lyapunov’s central limit theorem, we hypothesize that the distribution of can be theoretically approximated by a reciprocal–normal distribution. We show that a non‐normal and skewed distribution of is to be expected and is not a sign of measurement error or sampling bias, although sampling bias can exaggerate such skewness. Our framework also enables us to propose the mode as a characteristic value of measurements, as opposed to the mean or median, which can overestimate the most probable value.