Probably it is late for starting from seeds at this time, in your zone, outside. Your best bet is to get "sets", sold at most nurseries, HDAlthough, you can start your seeds inside, to get a head start. I am not an onions experts by no means but to me yellow spanish/granex? has done well. I have still have some from last year.They were mostly small and medium, not very big.
Red variety, on the other hand (don't know the variety) were bigger but did not store well.

The safest bet for Virginia will be the intermediate day onions. I had good luck with Spanish types in southwest Virginia, but June and July there is much cooler than the tidewater area. Most storage onions are very long day and better suited for the northern part of the US. At this stage of the game, Your best bet will be to get plants either locally or from a vendor like Dixondale. The sets ( small dry bulbs) will be long day onions storage onions, but in Virginia are best for spring onions. They often do not bulb up well in the south.

Thanks farmerdilla. I will buy starts.

I don't know how much diffrence in day length will be, say, between Georgia and Connecticut?
Or maybe it is the summer temperatures that decide what kind to plant???
I planted onions for the first time last year. I bough these small onions from Pikes that I thinks were the sames as sold in grocery stores as PEARL ONIONS.I planted them late DEC or early JAN and harvested in July sometime. So what was that ? short day, long day, medium day ??
This year also I have done some similarly, plus I have planted some from seeds in October. And few days ago I planted some sets(from HD).
Pardon me! I am just a novice about growing onions. But considering, I did well last year; I am still cooking with my last years yellow onions.Not bad, ha.

cyrus, while daylenght is somewaht longer is measurably longer as one goes north, even in GA the daylenght is sufficient at summer solstice for many of the long day onions. The problem becomes the triple digit temperatures which come with it. We have winters mild enough to grow short day onions which are harvested in April. I use to grow Spanish types in mountains of south west Virginia and they did quite well. One of the towns there was noted for passing out free lemonade to all visitors if the temp ever reach 90 degrees at any time during the summer.

Thanks Farmerdilla,
I thing I got it now: "Temperatures"
Last year I harvested my onions in late june/early July. I am in north Atlanta/Alpharetta area. I have become an onio enthusiast, as it is economical to grow. I just bought some more small onions from Walmart today(pearl like , not sets). But It is tooo cold to work outside right now.
When I have plenty, I plant them closely and thin them by using those as scallions. I cannot imagine cooking anything and not using onions and garlics. That is why to me its worth it growing them. The younger ones , from seeds are just like chive too.