Winter squash and summer squash belong to the same gourd family, but they have different storage needs, freezing excepted. With their thin skins and high water content, summer squash, such as crookneck, pattypan and zucchini, spoil more rapidly than winter squash, like acorn, butternut or delicata, which have hard, thick skins that protect the flesh.
Stored in a cool dry spot, such as a pantry without heat or a low drawer in your kitchen, whole winter squash stay fresh for 1 to 2 months, with no wrapping necessary. In fact, refrigerating winter squash changes the texture and flavor of these squash for the worse. On the other hand, summer squash need refrigeration as soon as you get them home from the store; these squash stay fresh, wrapped in plastic, for about 4 to 5 days.
Whether you buy them already cut or you cut them after you get home, refrigerate cut, raw squash of all types to keep them fresh. The cold temperatures in your fridge slow down the effects of air, which suck moisture from the vegetables; and slow down the growth of bacteria. Wrapped in plastic, winter squash stay fresh for 2 to 4 days and summer squash for 2 to 3 days.
Once cooked, winter and summer squash stay fresh in the refrigerator for 3 to 5 days whether you cook them whole or have pieces left over from dinner. Refrigerate the squash after cooking, well wrapped in plastic, letting whole squash cool slightly. Place these still warm squash in the coldest section of the fridge, on the bottom shelf, so they will cool quickly, and use the cooked leftovers in salads, soups, omelets or casseroles.
Cooked or raw, summer or winter varieties, whole or in pieces, squash keep in the freezer for 10 to 12 months. Casseroles with squash keep for the same time as well. Raw squash pieces retain more flavor and texture if you prepare them carefully by blanching them before freezing. Cook these pieces in boiling water for about 3 minutes, then plunge them into a bowl you've filled with ice cubes and water to stop the cooking. Pat the pieces dry, then wrap tightly in a freezer bag or double wrapped in plastic and foil.