Oranges are ripe when the fruit feels firm and heavy for its size. Skin color is not a sign of ripeness in oranges. Oranges grown in the summer or in very warm climates still have green patches when they are ripe.
Ripe oranges are full of juice and have been on the tree long enough to develop a high sugar content. The easiest way to judge the ripeness of the orange is to pick up the fruit and feel it. If the skin feels loose or the fruit feels light, the orange flesh is likely to be dry. A smooth, firm skin with no soft spots and a solid, heavy feel shows that the orange is ripe and ready to be eaten.