Hi Marcia, I'm jealous I so totally should have planted watermelon this year too! Hope this helps! https://commonsensehome.com/tell-watermelon-is-ripe/
Hi Marcia. Ripe watermelons break easily from the vine when twisted. If you try to pick one and it fails to twist off easily, it probably isn't ripe yet. Another sign of ripeness is when the underside changes from white to rich yellow. Also, a good watermelon will seem heavy for it's size. This means that it was watered regularly and it has a lot of juice. Good luck Marcia.
Hi Marcia: Here are a couple of sites that may help:
If your watermellon doesn't taste sweet enough, what I do, and my friends all go "Ick" is to put a bit of salt on it. The salt brings out the sweetness:)
Dark green even color skin and a yellow oval circle it’s ready this has never failed me .