planting onion seeds for overwinter?

Onions are biennial. That means in the second season they go to seed. So onions may not be good plants to overwinter. Tomato plants can live for 3 years in tropical climates, so they overwinter well. Pepper plants are supposedly able to overwinter but I have not had any luck with them. Cucumbers also did not overwinter and broccoli plants broke. Brussel sprouts ovewintered but my sprouts were still only a half centimeter when the first snow came and killed the plants.

But you can still try. I'd be interested in how it works out.

Your planting zone says mid-April to Mid May but I suspect that is esablished seedlings. I see the subject says for over-wintering things, and I'm not sure of that.

My green onions and Tokyo bunching onions survive over winter

this is going to depend upon the variety of onion so i would guess for these sometime towards the end of July, you'll have to keep them moistened pretty much every day (but not sodden) to sprout and grow. whatever sprouts you get will grow a little and then get knocked back by the cold and you will have a tiny bulb which will resprout and finish in the spring. the problem is that if the little bulbs get too big and too stressed they may just bolt, flower and make more seeds instead of onion bulbs the next growing season.

you are much better off starting the seeds indoors in the beginning of the next year and then plant those starts out when the worst of the winter has passed.

songbird

Normal. Your main planting is as above per google.