Hi Northerner,
Do you live between Buffalo and Toronto? The odd weather you described fits here to a tee.
You can not cut the flowers and let them dry inside before the seeds are ripe. All you'll get are dry underdeveloped bad seed. What seeds you get for saving depends on a few things. Some annuals, if not complete toast, will keep on maturing seeds. Plants can have leaves turn to mush or sections of the plant die off, but can still be alive and sending signals, food, or what ever it is that plants do to the seeds. You just have to pray that another hard frost doesn't come along too soon that makes the whole plant die.
Hardy perennials like coneflower will keep on developing seeds after a frost or two. If you notice in you garden some of you perennials don't look damaged at all. They can tolerate a bit of bad weather.
So no one unless they come over and actually see the damage will be able to tell you exactly what you'll get seeds from. But I hope from what I wrote, you can assess the situation better.
For future years, when you know an early frost is coming and you are waiting on seeds, pull out some sheets and cover the plants for the night. When there is a frost warning also, know to take it serious of there is no cloud cover. A starry night will get colder than a cloudy one.
Remy

Thanks for coming to my rescue, Remy. I actually live in Ottawa which is Northand East of Toronto, but it seems most of Ontario had this awful weather this summer.

I understand what you have told me about the ripening of seeds and there may be a few zinnias which have ripe enough seeds. I will leave the Ech. Jade a bit longer and see what develops. But I will certaily lose my beans (romano and Scarlet Runner) because they are too green. Also no seed from Datura (pods still green), Hibiscus, or Yvonne's Salvia.

The first frost was not a hard frost,not particularly early for these climes, but it was totally unexpected. I had a Brug., full of buds for the first year just ready to pop and I had an old sheet to cover it when the first frost warnings were announced. But the weatherman was quite wrong, so the frost was unexpected. We have since had two hard frosts so everything is toast. I collected some perennial seeds today and lifted some tubers to over-winter. Now I'm off to scour the exchange site so I can see what's out there for the taking. Thanks again.
Northerner.

Hi again Northerner,
Too bad about the crummy weather reporting! It does help though to notice the sky like I said. If they say upper 30's and the sky is clear, I might not trust them again.
I'm sorry you've lost so much : ( Some years are like that. In 2006 we had a freak snowstorm on Oct. 13. Everything got wiped out and I had hardly any seeds. The generosity of traders around this place though is amazing and I still managed to receive more seeds than I could possibly use.
Remy