Sets are notorious for bolting. However if you have a cool wet season sometimes a significant number will bulb properly. The varieties are all somewhat small storage onions, so don't expect jumbos. Most of us use them as scallions (spring green onions). They may need some protection if you ground stays frozen all winter. I have only planted them at the spring thaw.

farmerdilla-
Thanks for the info! They are in a short raised bed, and are mulched with straw. I've also put a thick concrete blanket over the top, so that my recently planted garlic can settle in a bit before the ground permanently freezes.

Can you explain to me what happens when an onion bolts? Does it just produce flowers, or is it the bolting that produces sets?

An onion bulb is a cluster of modified leaves. The rings each represent the base of a leaf. Lots of big leaves equal big onions. When they get ready to reproduce, they send up a thick hard stalk. A flower head and subsequently seeds form at the tip of the stalk.The seed stalk extends to the root causing what bulb forms to be hollow.