Due to warmer winter and spring, row crop planting has been relatively early in South Dakota. As of May 17, 2026, 80% of corn was planted with almost 20% reported to be emerged (USDA, NASS). Soybean plantings were reported at 60% with 10% emerged (USDA-NASS). Early planting may increase yield potential in some years but also puts crops at risk for damage caused by early-season or late spring low temperatures. Several days with temperatures lower than 32 °F were observed in the last two weeks. While a relatively low percentage of crops planted are likely to emerge this time of the year, producers may still want to evaluate individual fields for crop damage. Some locations (especially low-lying areas) will likely see lower temperatures than those recorded by the weather stations.
Impacts on Plant Growth
One common question we face is: what is the difference between a frost and a freeze? A frost event occurs when the temperature of the soil surface is 32° F or lower, while a freeze occurs when the air temperature is 32° F or lower at five feet above ground level. It is important to remember that, if atmospheric conditions are right, it is possible for frost to occur even when air temperatures are slightly higher than freezing. While mild frost should cause minimal damage to young crops, a hard freeze (28° F or colder for 2 hours) will most likely be damaging if not lethal.
The growing point of corn plants remain below the soil surface until V6 growth stage (the plant is approximately 1’ in height) and is generally considered safe from freezing air temperatures. However, if air temperatures remain below 28°F for more than a few hours, the growing point may be injured or killed regardless, as the lethal cold may penetrate the upper inch of soil. This is more of a concern when soil conditions are dry.
Source : sdstate.edu