Water molecules were assigned to the nucleic acid hydration shell and to specific sites on the biomolecule following simple geometric criteria (see details in SI). Site-resolved hydration reorientation dynamics was then quantified with the reorientation time τ reor , obtained by numerical integration of the reorientation time-correlation function averaged over the ensemble of water molecules initially assigned to each site. The retardation factor ρ reor quantifies the slowdown in hydration dynamics with respect to the bulk. This strategy allowed us to obtain spatially resolved maps of hydration dynamics of the DNA and RNA double helices under study (Figure ). While earlier simulation studies, with limited statistics, relied on averaging water dynamics over equivalent sites in different base pairs along the sequence, our simulations are long enough to allow examination of converged dynamical properties at a single-site level, as demonstrated by the estimated error bars associated with the computed single-site jump and reorientation times (see SI), that are much smaller than the variations that we will discuss.