  We demonstrate that dark matter heating of gas clouds hundreds of parsecs
from the Milky Way Galactic center provides a powerful new test of dark matter
interactions. To illustrate, we set a leading bound on nucleon scattering for
10-100 MeV mass dark matter. We also constrain millicharged dark matter models,
including those proposed to match the recent EDGES 21 cm absorption anomaly.
For Galactic center gas clouds, galactic fields' magnetic deflection of
electromagnetically charged dark matter is mitigated, because the magnetic
fields around the Galactic center are poloidal, as opposed to being aligned
parallel to the Milky Way disk. We discuss prospects for detecting dark matter
using a population of Galactic center gas clouds warmed by dark matter.
