  If millicharged particles (MCPs) exist they can be created in the atmosphere
when high energy cosmic rays collide with nuclei and could subsequently be
detected at neutrino experiments. We extend previous work, which considered
MCPs from decays of light mesons and proton bremsstrahlung, by including
production from $\Upsilon$ meson decays and the Drell-Yan process. MCPs with
masses below a GeV primarily arise from proton bremsstrahlung, while heavier
MCPs predominantly originate from heavy meson decays and Drell-Yan. We analyse
the resulting single scatter and multiple scatter signals at SuperK and JUNO.
Searches for low energy coincident signals at JUNO will be sensitive to MCPs
with milli-charges up to an order of magnitude beyond current constraints for
MCP masses between 2 GeV and 10 GeV.
