It is still early, but in just a few short months plants will be growing and gardens will be producing.  People often want to know when the right time is to pick their watermelons.  There are several ways to determine this, and here are a few.

You could always cut into one.  The only down side of this method is that there is no turning back if the melon isn't ripe (so you may only want to use this method if you have extras that you don't care about).  Many people check the stem or tendril by the melon.  If it is turning brown or is completely dead where the stem meets the melon, then the melon should be ripe (or at least close).  You can also check the underbelly of the melon to see if it is a creamy yellowish color (if it is then it is probably getting ripe).  Some people will keep track of the time or number of days from the time of flowering.  This is a good way if you have a good memory or if you are good at keeping track of notes.  If all else fails, you can always thump the watermelon.  This may take practice.  You are wanting to hear a thud that is a little hollow sounding.  If it is a really low thud or a very hollow sound then it may be over ripe.