If soybeans finally succumb to a freeze, they're done. They don't have the ability to regrow like corn. The growing point for soybeans is above the ground as soon as the cotyledons break through the soil. For corn, the growing point remains below ground until about the six-leaf stage. So if corn leaves are destroyed on a young plant, the growing point can still keep the plant alive, and it has the chance to continue growing, and eventually produce a good crop.
This difference in agronomic traits has led many over the years to believe that if it frosts, soybeans are done. Trials several years ago at Purdue University, repeated in the late '90s by Indiana Prairie Farmer with the help of Beck's Hybrids, using Purdue's chiller facilities provided through the Purdue Agronomy Department, prove that it takes much more than a frost to knock out soybeans. They can withstand much colder temperatures than corn before the seedlings succumb.
In fact a 32 degree reading, especially if it only lasts a couple hours, won't harm most soybeans. Most varieties can survive 28 degrees for two to four hours,. It's not until you reach 24 to 26 degrees F, and hold it there for two to four hours, that soybean seedlings begin to die due to freeze injury. That's based upon the varieties that were commonly planted when these tests were conducted. Since the last one was more than a decade ago, it's unknown, or at least not reported, if today's varieties are more or less susceptible to frost and freeze damage than those of earlier days.
Due to the nature of late spring frosts and /or freezes, timing becomes important. Sometimes the coolest conditions don't develop until early in the morning, sometimes before sunrise. How much damage the cool weather will do depends upon when the cold temperatures occur and how long they last.