It is so hot. It's hot in the sun, it's even hot in the shade. We hear repeatedly that we need to help our little Ones stay cool by dressing them wisely in light-colored clothing, but why not let them explore the "why" behind that idea? In other words, turn the daily clothing battle into a learning experience that's meaningful to them.
In a nutshell, the reason for this is that dark colored clothes ABSORB light/heat which make the person even warmer. Light/white clothes REFLECT light/heat and therefore keep a person feeling relatively cooler.
Now, see if your child really gets it by asking him which color clothing he should wear outside in the winter!