First, it is tried factor analysis to observe that options development for some factor among weather element is available. And attempted multi-regression analysis between factor score and stock index to confirm necessity of weather derivatives development. Prior to pricing of weather options, it is very important to decide a stochastic model for weather element. Stochastic model for weather element is presumed adding error term that have stochastic process applying deterministic model about average temperature that Alton, Djehicle, Stilberger(2002) present. And selection of data period for model conclusion is decided through Akaike information criteria and Schwarz standard. After stochastic model is selected, drived theoretical price by monte carlo simulation In this study, it is decided on weather options price against full Korea area using weigh-averaged weather data by estimated population of metropolitan city as well as weather data of a Seoul.