  We theoretically propose a family of structurally stable monolayer halide
perovskite A$_3$B$_2$C$_9$ (A=Rb, Cs; B=Pd, Pt; C=Cl, Br) with easy
magnetization planes. These materials are all half-metals with large spin gaps
over 1~eV accompanying with a single spin Dirac point located at K point. When
the spin-orbit coupling is switched on, we further show that
Rb$_3$Pt$_2$Cl$_9$, Cs$_3$Pd$_2$Cl$_9$, and Cs$_3$Pt$_2$Cl$_9$ monolayers can
open up large band gaps from 63 to 103 meV to harbor quantum anomalous Hall
effect with Chern numbers of $\mathcal{C}=\pm1$, whenever the mirror symmetry
is broken by the in-plane magnetization. The corresponding
Berezinskii-Kosterlitz-Thouless transition temperatures are over 248~K. Our
findings provide a potentially realizable platform to explore quantum anomalous
Hall effect and spintronics at high temperatures.
