A method to estimate meteorological factors on a 250 m square grid using real-time data from a local weather station network was developed. The method had better precision than an existing one. The 250 m square grid meteorological information was created to cover Memuro City, Hokkaido. The information was used with a wheat developmental model to predict the distribution of wheat maturity days in the city, which had 6, 170 ha of wheat fields and 50 combine harvesters, to support decisions for the best management of the harvesters to avoid damage by preharvest sprouting.