1991-2020 averages for temperature, precipitation, frost-free season (80-365 days by region).
GDD formula and base temperatures. Corn needs 2,200-2,800 GDD, soybeans 2,200-2,900, wheat 1,800-2,200.
Match crop maturity class to available GDD by region and elevation.
5-step framework integrating frost dates, GDD, hardiness zones, and precipitation.