My onions never fully top down like the texts describe. They are usually green and growing through the end of summer. So I usually pull them in the end of august at the start of a sunny dry stretch. Spread them out on the lawn for a few days to "cure" then hang them in the basement to finish curing.

Since you don't really have the option of setting them in the sun now, I would jut pull them and tie them up somewhere so they can cure. Which is essentially drying out. Make sure to eat the ones with the thickest necks first and any that started to flower. These will not store as long.

I break the tops of mine by bending them over, then let them cure in the ground. Like Whitman said, be sure to eat the large neck and flowering ones first.

Even in the midwest, my father always bent them over- went down the rows and stepped on them to get the tops to stop growing and brown off. It was a long time ago and I don't remember when he did this, either when in the growth cycle or when in the calendar year.
But then somewhat after, he pulled them and set them on tables outin the sun to dry off. My job was to turn them each day.
Once dry he braided them into chains to hang in the garage or basement.