It depends. Many plants overwinter in rosettes the first year, even some native annuals, like bluebonnet and american basket flower. Without knowing all sort of information (like what plants), location/climate, and doing a lot of research, no one will be able to tell you.

And ultimately, you just have to wait and see, what else CAN you do?

We don’t know your location so we don’t know what your winters are like. We also don’t know what seed you sowed. If the perennials are hardy in your location they presumably have the potential to survive the temperatures but there are other criteria such as wet and pests. As dbarron says what can you do other than waiting and seeing?

Thank you both. More detail: I'm Zone 5a/6b, Litchfield County CT. The seeds I scattered were a wide selection of drought-tolerant perennials, purchased from High Country Seeds: echinacea, gaillardia, coreopsis, penstemon, and so on. Some seeds, I know, have a built-in protection against premature germination, requiring freezing temperatures before they will germinate. But others, as I see, take the first opportunity to sprout. I hope they aren't doomed because they jumped the gun. Just wondering what experience other gardeners might have had. Thanks again for your responses.

At a guess they'd be ok, but this is why it's best to buy separate species, that way you know for sure proper planting protocols to avoid such problems.

Of course, in "nature" seeds are regularly dropped long before the end of warm weather.

That's not exactly accurate. Even in the northeast, there are plenty of plants that drop seed well into autumn and even into early winter.

I think it would really depend on your weather. Now, if they were exposed to wind and sharp cold, I think this would tend to do them in. Where as, if you'd soon receive a consistent insulating layer of snow it would go a long ways in protecting them. I have very harsh winters, way worse than yours, though when snows come early and it sticks and stay, it's amazing what can make it through the winter.

Mad gallica said exactly what I was thinking. Some, not all, of the various species I bought from High Country Gardens have survived, but many haven’t survived the winter, not because of cold, but due to moisture, even in my sandy soil. So as others have said, you will need to wait to see what survives. Just be aware that even mature plants from the desert may not like our eastern winter moisture, so what doesn’t survive is more likely the wet as opposed to the plant maturity.

Good point, considering the extreme rainy weather we've been having here in recent weeks. But this planted area is TRULY droughty and I'm hopeful. A snow blanket would certainly help too, as FrozeBudd says. However, I still have half a bag of those seeds left, and I expect another scattering in late March will be backup plan.

Which mix did you buy? The website shows many and not all are 'western' seed mixes. They have midwest, eastern, southeast etc.