Predicting the barriers to electronic excitation and charge transfer is essential for engineering materials for solar cells, mimicking redox processes in enzymes, and building molecular electronic devices. Advances in electronic structure theory have enabled accurate descriptions of electronic states and the couplings between them, facilitating in silico design and screening of potential next-generation molecular devices. However, most work on predicting molecular properties such as vertical excitation energies, polarizabilities, or single-molecule conductances is limited to equilibrium geometries, ignoring effects of nuclear motion. This approach works well when the coupling between electronic states and nuclear motion is small and symmetric. In other words, if movement in direction +Q and -Q (which can be represented as a linear combination of normal modes Qi) changes some property by a small amount +δ and -δ, respectively, the effect of nuclear motion can be approximated by a mere broadening (proportional to dδ/dQ) of the observed property.