It seems it has to do with how much water the watermelon has soaked in a given time interval:
http://who-what-where-when-how-why.blogspot.com/2011/09/why-do-watermelons-crack-split-open.html
And some types of watermelons are thin-skinned and have a higher propension to split easily.
The article link above states that it might also have to do with pesticides and fertilizers, but I doubt it applies to watermelons here in North America.
WATERMELONS ORIGONATE FROM THE AFRICAN DESERTS
watermelons arent always organic
the mass of 10 watermelons is 90kg
brains, watermelons
The city of Hermiston, Oregon is famous for their watermelons.
yes, watermelons do have vitamins. they have vitamin A and C for eysight and the brain.
watermelons command name is a fruit or a green fruit
The country that plants the most watermelons is China
He really doesn't hate watermelons. It is a joke for his show, Mail Call. He often uses watermelons as targets for weapons demonstrations.
I do!
Yes, you should be able to grow watermelons in your home garden
Yes, watermelons do have flowers during their growth cycle.