How do you know when watermelons are ripe?
Over the years I heard of and tried many melon ripe tests. It's sometimes best to combine several of them to judge a good melon. Knowing which variety might help a bit but here's the general "rules":
Thumping a melon with middle finger or knuckle and listen to the pitch : "pink" sound is unripe, "punk" sound might be ripe.
Try this out on several melons to adjust your ear to the different pitches (high=pink, low=punk).
Tendrils - those curly things, if the tendril on each side of the melon has dried up and shriveled it could be ripe.
Luster of surface of melon. If it's glossy it's unripe, if it's dull it might be ripe.
Smoothness of surface of melon. If it's smooth as a cueball it's unripe, if it's slightly "bumpy" it might be ripe.
Size, if the size stops increasing for 2 weeks it could be ripe.
Bottom color of melon, if it's white it's not ripe, if it's light yellow it might be ripe (except for Sugar Baby variety which is always a deep yellow).
Bottom "specks", if black specks/spots are within the bottom light yellow color it might be ripe.
I hope these help you, they have given me a 95% goal of picking ripe melons, esp if combined together. One last tip, if in doubt wait a few more days. I say this because an unripe melon is usually terrible but an over ripe one is usually mostly edible. Oh, and one more tip, the sweetest melons ripen during a dry spell so don't water the melons 2 weeks before you think it getting close to picking.
Happy Harvest !