In the southern United States, the alligator snapping turtle (Macrochelys temminckii) is the largest freshwater turtle in the world by weight. Females dig nests and lay between 10 and 50 eggs in late spring and early summer. Hatchlings emerge in early fall.
It has been observed that most or all of the M. temminckii hatchlings are male if the summer is unusually cool. Most or all of the hatchlings tend to be female if the summer is unusually warm.
Which of the following BEST explains this observation?