Total darkness is required till germination occures.... lightly cover seed with soil then cover with black plastic.. soil temp 68-72F & takes 7-21 days to germinate

I gave up on growing onions from seed long ago. They germinated OK, but the seedlings are so delicate that they are subject to damage and infant mortality. Most seeds do not need light to germinate, but they need to be moved close to a flourescent light as soon a sprouting or they will become really leggy. Some small seeds like lettuce need light to germinarte well. Otherwise same rules apply.
I start most seeds in peat pellets or soilless mix. most seeds germinate well at about 75 degrees. Some like peas will germinate in the 40's. Just put Growing from seed in your browser and you will get all of the info you can handle.

Little scrawny onion plants the size of spaghetti will still make good size onions here in Indiana. Plant them out early, late april to early may. You can go a couple weeks before the last frost date with them. Don't give up on them, just because they are small... I've found in my greenhouse though, I have to plant them very early, like January, to get good size plants. I have been growing "utah sweet spanish" for the last three years from seed. I usually start them in a shallow flat of seedstarting mix, then transplant them to a good mix like promix hp, in a deeper flat when they are big enough to handle easily, a month or two. Then use 20-20-20 peters professional on them at 1 t per gallon, and 1 T vinegar every watering. They need lots of light. They can still grow with pretty cool temps, down to 50 at night or even a little lower.
Last year, my onions were a little smaller than usual, most were the size of a baseball though!

I started my onions in January, they took about 2 weeks for germination, they have been under lights but seem to be suffering from tip die back. They are very fragile, I have been watering with a weak fertilizer weekly. I have lost most of them.

I sowed my seeds in rows in the garden in mid-October. As the onions grew, I would thin and move plants, now I am to the stage of thin and EAT thinnings!

They are easy in the ground, but you would probably have to start in the spring where you are.

Janie