For regular turnips it may be a little late, but Hakurei turnips would work very well. All those crops you listed are frost-tolerant, so you have way more than 60 days. The spinach and kale are particularly tolerant and will be fine right until the first permanent snowfall.

OTOH, you have to add a 25-50% extension to the DTM to account for fall's shorter and ever-shortening days.

I would also suggest radishes, tatsoi, bok choy, gai lan and claytonia.

IME, freeze damage thresholds are about like this (this is without row covers):
Least tolerant: lettuce and bok choy - mid to high 20s F
Tolerant: beets, turnips, radishes - mid 20s F. Mound up soil around the growing root to prevent the root from freezing.
Very tolerant: kale, spinach, tatsoi, claytonia - mid teens F

This post was edited by Slimy_Okra on Fri, Aug 15, 14 at 21:48

concur and add arugula to the list.

I just planted some lettuce seeds yesterday. I plan to plant spinach and bok choy in a few days. Our first frost date is Oct 21. I ordered some lacinato kale seeds and hope they come in soon.