1 Temperature influence on growth – Seeds of cool season crops germinate at 40°F to 80°F. Warm season crop seeds germinate at 50°F to 90°F. 2  In the spring, cool soil temperatures are a limiting factor for plant growth.3  In mid-summer, hot soil temperatures may prohibit seed germination. Temperature influence on growth – Seeds of cool season crops germinate at 40°F to 80°F. Warm season crop seeds germinate at 50°F to 90°F. 2  In the spring, cool soil temperatures are a limiting factor for plant growth.