Well, it happened. An early frost.
I was completely oblivious to there being any frost danger - it's still August after all! Even in this part of Alberta, August is not typically a time to worry about frost. But this morning I ran out to see the pumpkins that Gord said were growing in the garden (I had thought all hope of pumpkins was lost), and then noticed that the pumpkin leaves were all soggy and limp. Then I cast my eyes to the squash patch, and yup, those leaves were soggy and limp too. Those are the soggy squash leaves in the picture there, with one brave butternut squash among them.
I have no idea if the squash or pumpkins will now get any bigger, without leafy solar collectors to make sugar. The one bright spot is that the part of the squash plant that had curled its way in between the corn rows didn't get killed by frost. So maybe those few leaves might sustain the a few squash and let them grow a bit more. I don't think the apple-sized green pumpkins will be so lucky though.
The kale, beets, chard and spinach I planted came through alright, this time. I will have to be more aware of night time temperatures from now on, and get going on my plan to cobble up some row coverings or cold frames or something so these newer plantings can keep growing for a while yet. It's a good thing we're coming up to a long weekend, because I've obviously got some work to do!