The polarization reversal induced by infrared pulse laser irradiation at elevated wafer temperatures was studied in single crystalline congruent lithium niobate LiNbO3. The temperature dependence of the statistical parameters of the formed self-assembled nanoscale domain structures was extracted. The obtained behavior was attributed to formation of nanodomain structures due to “discrete switching” under the action of pyroelectric field taking into account ineffective screening of depolarization field.