In Season: Most supermarkets carry them year-round, but peak growing season in North America is July to December.
What to Look For: Grapes should be plump, with smooth unbroken skins, and be firmly attached to the stems. The green ones are at their sweetest when they have a pale-yellow hue. Often, grapes are covered with a whitish "bloom," which is a natural protection against loss of moisture and spoilage.
How to Store: Discard damaged grapes, place bunch in a plastic bag, and refrigerate up to three days. To avoid destroying the bloom, rinse just before using.