That would be "freeze"

Definitely not an expert here, but since mine reseed every year by themselves in my zone 4 with plenty of freezing and thawing, I would guess yes, they will geminate.

Let us know if you find out!

Thank you hydrangeahead, my area went down to -9'c one night, commonly -3'c. I saw yesterday (2018.05.02) that I have two seedlings, I hope for more. I'm guessing I would have more if I lightly cultivated the area after seed fall but before it gets really frosty

I planted 'Heavenly Blue' and 'Grandpa Otts' morning glories in my garden about 8 years ago. While beautiful, I regret it to this day. Every year hundreds of morning glories come up from seed (self sowed). I try to pull out every seedling I find but a few make it up my tomato vines and I do not find them until the are blooming. I try real hard to eradicate them but no luck. I think the seeds that fall must not all germinate the following year as I have been super diligent in pulling out every seedling I find and still I have them coming up again this year. Now they are coming up in my rhubarb patch that is a good 15' away from my vegetable garden.

I enjoy free seedlings (my snapdragons come up by themselves for 19 years now as self seed) and dill seems to come up in the garden too along with volunteer tomatoes and some volunteer potatoes I must have missed from a previous crop.

Morning glories however are the curse of my garden since they come back each year by the hundreds.