Onions follow the changing day length closely, and they will bulb when day length and other environmental triggers tell them to. This late you can still put sets in the ground and pull them as green onions until they go by, plus there are bunching scallions to consider.

Zone 8 usually means a short-day climate as far as bulb onions are concerned, which means planting in fall for a good spring harvest.

Thanks, but my question was:
Does pulling them early still allow to get a nice storage skin on them. In other words, will I get that nice papery outer layer that mature onions get?

If they are still growing. No. Depends on where you are whether they will mature. Zone 8 in the south is too hot for onions and they will burn out in July. Short day onions will have matured, but long day onions will probably burn out before sizing up.

Yes, they will form skins anytime during their growth process. When people consider onions mature, it's only saying that they will not get any bigger. But I believe there is nothing in the chemical makeup that changes. So, pull them when you have to and let them cure and no matter how big they are, they WILL form skins.

I also agree that they'll form nice skins if cured well. On a previous post I stated that some of my smaller neglected shallots shut off early during our warm spring here this year and I'm actually curing them right now. They are little things about 1/4" - 3/4" in diameter. Your onions will probably be bigger depending on the type. Plus, another thing, onion sets are cured young onions for planting... So yes, they won't be as large but you could cure and eat them.