After harvesting, cure Waltham Butternut squash by keeping them in a sunny spot for 10 days to toughen the skin. Then, store them in a cool, dry place with good air circulation, ideally between 50-55°F (10-13°C). Avoid storing squash in humid conditions, and check periodically for any signs of spoilage. When stored correctly, Waltham Butternut squash can last several months, providing your family with a nutritious and delicious food source through the winter.