  We study strained Hg$_{1-x-y}$Cd$_x$Mn$_y$Te in a magnetic field using a
$\bm{k}\cdot\bm{p}$ model and predict that the system is a Weyl semimetal with
two nodes in an experimentally reasonable region of the phase diagram. We also
predict two signatures of the Weyl semimetal phase which arise from tunability
of the Weyl node splitting. First, we find that the Hall conductivity is
proportional to the average Mn ion spin and thus is strongly temperature
dependent. Second, we find an unusual magnetic field angle dependence of the
Hall conductivity; in particular, we predict a peak in $\sigma_{xy}$ as a
function of field angle in the $xz$-plane and a finite $\sigma_{yz}$ as the
$x$-component of the field goes to 0.
