Harvest winter squash when the fruit are fully mature. Mature winter squash have very hard skins that can't be punctured with your thumbnail. Additionally, mature winter squash have dull-looking surfaces.
When harvesting winter squash, handle them carefully to avoid cuts and bruises. These injuries are not only unsightly, they provide entrances for various rot-producing organisms. Cut the fruit off the vine with a pruning shears. Leave a 1-inch stem on each fruit.
After harvesting, cure winter squash (except for the acorn types) at a temperature of 80 to 85 degrees Fahrenheit and a relative humidity of 80 to 85 percent. Curing helps to harden their skins and heal any cuts and scratches. Do not cure acorn squash. The high temperature and relative humidity during the curing process actually reduce the quality and storage life of acorn squash.
After curing, store winter squash in a cool, dry, well-ventilated location. Storage temperatures should be 50 to 55 degrees Fahrenheit. Do not store squash near apples, pears, or other ripening fruit. Ripening fruit release ethylene gas which shortens the storage life of squash.
When properly cured and stored, the storage lives of acorn, butternut, and hubbard squash are approximately 5 to 8 weeks, 2 to 3 months, and 5 to 6 months, respectively.