Ditto what everyone else says. I am sure there is a low cut off, but it is more dealing with footing than anything.
I was just out in -4c the other day (which is just below 32f). In truth I was a little cold, but this is more due to how hard I am pushing myself (not hard at all) right now.
I would have been fine with a thin pair of gloves and a hat. My covered body did infact break a light sweat.
These guys have some good points...
Winter Running - Cold Weather Running Safety Tips
I have seen the dress for 20 degrees warmer than it really is, thing before.