Twelve Hats for Lena by Karen Katz
This is Not My Hat by Jon Klassen
A general discussion could be held about how hats keep heat in our bodies or how hats provide shade.
Look under Early Science in the link below for an activity idea:
Note 1: Twelve Hats for Lena lends itself to a discussion of seasons and the calendar year.
Note 2: This Is Not My Hat easily sparks a discussion of predators, prey and the food chain.