Probably the most important indicator of ripeness is the underside which sets on the ground. Turn the melon over. It should be yellow or creamy colored on the underside. If it is white or pale green the melon is not ready to harvest. The flesh should be deep colored with mature seeds.
Most watermelons have dark brown or black seeds.
The seedless variety produces a few white seeds. Uncut watermelons have a shorter refrigerator life, so store at room temperature until ready to chill and eat. Tightly cover cut pieces in plastic wrap and store in the refrigerator for 2 to 3 days. Watermelons are low in calories and very nutritious. Watermelon is high in lycopene, second only to tomatoes.