  We use high-resolution, hydrodynamic, galaxy simulations from the Latte suite
of FIRE-2 simulations to investigate the inherent variation of dark matter in
sub-sampled regions around the Solar Circle of a Milky Way-type analogue galaxy
and its impact on direct dark matter detection. These simulations show that the
baryonic backreaction, as well as the assembly history of substructures, has
lasting impacts on the dark matter's spatial and velocity distributions. These
are experienced as 'gusts' of dark matter wind around the Solar Circle,
potentially complicating interpretations of direct detection experiments on
Earth. We find that the velocity distribution function in the galactocentric
frame shows strong deviations from the Maxwell Boltzmann form typically assumed
in the fiducial Standard Halo Model, indicating the presence of high-velocity
substructures. By introducing a new numerical integration technique which
removes any dependencies on the Standard Halo Model, we generate event-rate
predictions for both single-element Germanium and compound Sodium Iodide
detectors, and explore how the variability of dark matter around the Solar
Circle influences annual modulation signal predictions. We find that these
velocity substructures contribute additional astrophysical uncertainty to the
interpretation of event rates, although their impact on summary statistics such
as the peak day of annual modulation is generally low.
