The atmospheric dispersion characteristics in the vicinity of a nuclear power plant are important in establishing criteria for safety features, reactor containment, and site boundaries so that there is reasonable assurance that radiation dose guidelines would not be exceeded should a major accident occur. Large quantities of meteorological data are now available from many sites which provide a good statistical base for evaluating the effect of local site weather conditions on the total dose risk. A model has been developed for determining dose level versus probability based on combining time variant weather data with the time variant fission product release following an accident. The results obtained using this model to evaluate several sites indicate that the probability of any individual receiving a dose in excess of regulatory guidelines is quite low, given that an accident has occurred and that the resulting fission product releases are evaluated using conservative AEC licensing assumptions. These results also show a large variation in dose among facilities at a given probability level. Other applications of this model for evaluating doses due to hydrogen purging, for predicting the most faborable time to make routine effluent releases, and for assessing total dose risk of a given site are also discussed.