You can be on the frosts edge. A few trees in a dip. Or trees boxed in by mature trees can frost and the others dont. Areas shaded in the afternoon can frost too.
Trees near water can be saved from a frost too. The heat from the water keeps the locale a touch warmer.
Variety is the spice of life. Some trees bloom later. Also, soil temps can effect bloom too. Variances in soil depth, compactness, distance to water table, and insulating mulch can make a tree bloom later too.
One guy by me lays tons of wood chips. He thinks they bloom later because of it. Seems they do...