So, if freezing cold follows the warm spell, the result can be a rather drab spring. The plants that thrive in our temperature zone need a certain amount of cold each year. Generally, we think of that requirement in terms of number of days with temperatures in the 32 to 45 degree F range. Until their need gets met, plants won't break dormancy, no matter how warm it gets. The results of late-winter warm spells are less dependable, however.
Some plants tend to bud out earlier than others.
Different plants' buds vary in how 'tough' they are. Harsh cold can kill. It also can slow new growth, but leave it largely unfazed. Typically, what gets caught first is the flowers on some established trees and shrubs. Apples, crabapples and forsythias have tougher buds.