The meteorological conditions for grasshopper disasters from 1980 to 2004 in Inner Mongolia grasslands are studied. Results indicate that droughts in summer and fall and winter warming are advantageous to the survival of the overwintering grasshopper eggs, and the snow cover in winter can protect the eggs, but heavy snow at the end of spring would be fatal to grasshoppers. Rich rainfall in spring and gradually increasing temperature are favorable to the hatchability of grasshopper eggs. The emergence rate of nymphs can be reduced evidently when temperature drops strongly during the embryo and growth stages of eggs as nymphs cannot endure cold waves and heavy frost. After entering the fourth larval instar, grasshoppers begin to have the ability to avoid adverse conditions. The meteorological conditions before the growth stage of overwintering eggs and embryos and the third instar of nymphs have significant influence on the largescale outburst of grasshoppers, and thus can be used as good indicators in the early warning of grasshopper disasters.