My spaghetti squash and acorn squash vines are incredibly vigorous (my butternut squash, not so much), but so far most of the fruit has dropped off after flowering. All I've got to show for the season thus far is this one zaftig spaghetti squash pictured above, and two acorn squash. Having never grown winter squash before, I'm wondering: Is this normal?

Has the weather just been too cool to set fruit? Do I need to do some hand pollination? Or should I just be patient?