That is the major problem. Short days occur in cold weather so short day onions need some help in the frozen north. Several varieties have been successfully grown, Desert Sunrise for example. Overwintered but use low tunnels or something similar to avoid ground freezing.

Thank you. That makes sense. I've heard that short day onions make small bulbs up north because they start bulbing out before the greens are fully mature. That's what would happen if they were planted late enough that cold weather wasn't a serious issue. That is, they'd hit the short-day requirement for bulbing soon after planting.