Here we describe and experimentally confirm the localization of charged microparticles outside the area of a radio-frequency Paul trap. We consider the nonlinear effective potential formed by the trap, treating the field independently for different electrodes of the trap. To approach the proposed model to reality, we also consider the nonlinear effects originating from the viscousity of surrounding medium. Proposed approach allows to conduct an analytical description of the effective potential and define quasi-equilibrium points both inside and outside the trap. Predictions of the proposed model are in full compliance with obtained experimental results.