I've been out on a few cold dawn runs with the temperature around 4 or 5 degrees in the same gear as my summer runs and I've not been bothered by the temperature. In fact I've found the cold invigorating and appreciated not breaking into a sweat so quickly.
I have got a few pounds still to shift but I don't have that much blubber. So I really can't see the need for leggings, hats or running jackets. In fact I'm actively looking forward to my first run with a proper frost, surely I'm not the only one?