For instance, springs are very long and lovely in Portland, Oregon. In contrast, Midwestern springs are beautiful but more compacted in time because the winters are so cold and persistent, that even non-dormant plants will not grow until the outside weather is warm enough. Therefore, Midwestern fruit plants flower about the same time regardless of when their chilling needs had been satisfied. Once a plant's chilling requirement has been met, it is ready to grow, regardless of time of year. For this reason spring thaws and warm March weather can be disastrous to fruit growers.
Warm weather can induce premature growth which can be damaged by subsequent cold and frosts.
Remember, the growing season in Central Illinois does not begin until about May 12-15th, when the likelihood of frost has passed. Although the amount of chilling required to break dormancy has been investigated for many species, it can be difficult to find specific chilling requirements for some cultivars. Even when the chilling requirement is known, weather data is seldom presented in a way that growers can determine whether their crops have received sufficient chilling to commence growth. In addition, data is seldom available to predict a date when a particular crop should have received enough chilling hours to begin growing. Such information would allow growers to make better decisions about frost protection, pruning, and other cultural practices that could encourage flower development or succulent growth which are susceptible to cold damage.