  We develop an analytic model of thermal state-to-state rotationally inelastic
collisions of asymmetric-top molecules with closed-shell atoms in electric
fields, and apply it to the Ar--H$_2$O collision system. The predicted cross
sections as well as the steric asymmetry of the collisions show at fields up to
150 kV/cm characteristic field-dependent features which can be experimentally
tested. Particularly suitable candidates for such tests are the $0_{00} \to
2_{20}$ and $1_{01} \to 2_{21}$ channels, arising from the relaxation of the
field-free selection rules due to the hybridization of $J$ states. Averaging
over the $M'$ product channels is found to largely obliterate the orientation
effects brought about by the field.
