1. A method for estimating meteorological quantities, the method comprising: acquiring estimation conditions for meteorological quantities including historical data of meteorological quantities such as temperature and amount of rainfall observed in the past; acquiring an estimation period for estimating meteorological quantities at an estimation point; acquiring a number of times for a simulation; acquiring long-range weather forecast data provided by the Meteorological Agency for the meteorological quantities during the estimation period at the estimation point; creating a meteorological time-series model for the meteorological quantities during the estimation period at the estimation point based on acquired historical data of meteorological quantities and acquired long-range weather forecast data; conducting for the number of times the simulation using the meteorological time-series model; and outputting a meteorological quantities estimation result based on the simulation using the meteorological time-series model.