We developed a method for determining nationwide 1 km-grid square values of daily mean, maximum and minimum air temperature, and daily precipitation in Japan. The data were obtained using the JMA's nationwide observations, numerical forecasts, and climatic normal values. RMSE values for these elements in the past were 0.66 °C, 0.98 °C, 1.10 °C, and 5.9 mm/day, while those for one-day future were 1.18 °C, 1.65 °C, 2.00 °C, and 11.0 mm/day, respectively. The improvement in accuracy by introducing the forecasts was recognized even for values six-day future, though errors tended to increase with forecast range. The data are intended for use in the management of currently growing crops with a combination of crop models.