The Asiatic rice borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), is an important, widely distributed pest of rice, Oryza sativa L., in China. However, information is lacking about postdiapause levels of cold resistance during periods of normal development. Our results indicate that field larvae of C. suppressalis collected in March 2010 had very low survival if exposed to −21°C. When exposed to test temperatures for 1 h, the LTemp50 and LTemp90 values of C. suppressalis were −18.8 and −20.8°C, respectively. LTime50 and LTime90 values at −16°C (5.1 and 9.6 h) were unexpectedly lower than those at −17°C (7.1 and 18.3 h). For larvae collected in August, mortality at −18°C (with 2-h exposure) was 98% but was only 8% at −6°C (2-h exposure). Maximum cold tolerance of C. suppressalis was observed in larvae collected on 15 January 2011. These data suggest that cold hardiness in C. suppressalis is independent of the diapause state of the insect.