Nectarines are sometimes referred to as the fuzzless peach.  They have a recessive gene that  does not allow them to have fuzz. In fact, the flavor of some nectarines taste just like a peach.  Nectarines, are also summer fruit. Nectarines are a member of a rose family and closely related to almonds. It is one of the oldest of all fruits and apparently grew in China before the time of Christ. Look for a plump fruit with orange-yellow color between the red areas. Gently squeeze it in your palm. When fruit gave to little pressure it is ready to eat. If you buy firm to moderately hard Nectarines, they will ripen normally within 2-3 days at room temperature. Avoid hard, dull, or shriveled fruit. Nectarines should be held at 32-35 degrees F and high humidity. Fully ripened nectarines should be refrigerated immediately and kept there until ready for consumption. Sound and mature but not overripe nectarines can be expected to hold 1-2 weeks at 32-35 degrees F with little adverse effect. Nectarines deteriorate rapidly when stored for periods longer than this.

To ripen nectarines,  65-70 degrees F is best. There is no gain in sugar content once a nectarine is picked from a tree. Its ripening process consists primarily of softening, development of juiciness, and development of flavor. So the riper a nectarine is at harvest the more sugar it will contain. Remember, once a mature nectarine begins to ripen it never stops, but you can slow the rate of ripening by using low temperatures.

Here is a site for more nectarine information. http://www.nwcherries.com/nect.html