Why does BC say to protect from light?

I noticed on like 2 or 3 different BC's I've taken that on the package it says to store between like 68°- 77° and protect from light but why can't it be in light? Is it so it doesn't heat up? Is it just sunlight or light bulbs as well?

.

.

.

(Also how much does heat effect it, i live in Florida and our apartment doesn't have good air so its always 77°+ in my apartment. )