*sigh* my mom 5'3 and my dad is 5'5... and my gramps is 5'6... sucks, i want to be atleast 5'10 or atleast 5'11, but yeah my parents are short, but im not giving up.
Sunlight is important for vitamin D, because it is the most natural source god has given to humans. Sunlight is also shown to kill bacterias. But the fact that teenager sleep lot more in summer has to do more with growth. During school time, I get about 6 hours or less of sleep. In summer I get 10 or more hours. As you know deep sleep produces HGH. So that's why you grow more in the summer.