A study of satellite images of 85 large cities in the United States from 2001 to 2014 shows trees and vegetation in urban areas become green earlier but are less receptive to temperature change than rural regions due to an event known as the “heat island effect. The study reveals the start of the season appeared on average six days earlier in the reviewed cities than surrounding rural regions due to the heat island effect. Researchers are now seeking more accuracy in our earth system models to predict changes in our environment in the future. Considering the interactions between temperature and phenological variation in vegetation will mean those model predictions will progress.