Here is a typical winter layering system for myself...
(I don't normally wear this all at once, but I could)

Feet: (not reall sure of these weights)
thin wool socks 2oz
thick wool socks 4oz
felt insoles ( I won't count these but I would could felt liners if I was wearing my mukluks)
subtotal = 6oz

Bottoms:
Skin Layer 5oz
Intermediate Skin Layer normally reserved for sleeping 7oz
200wt fleece 12oz
Flannel Boxers (I won't count these because their cotton)
Rain/Wind Pants 6oz
Hiking Shorts (I won't count this 2nd shell)
subtotal: 5+7+12+6=30oz

Tops:
Skin Layer 6oz
Intermediate Skin Layer normally reserved for sleeping 9oz
light wool sweater 20oz
100wt fleece 10oz
Wind Shell 4oz
Rain Shell (I won't count this 2nd shell)
subtotal: 6+9+20oz+10+5=50oz

Hat/Mitts: (not reall sure of these weights)
Alpaca Wool Hat 2oz
Knit Lopi Wool Necky 2oz
Light Wool Gloves 2oz
Medium Wool Mitts 2oz
hood with rain shell, pockets used as overmitts
subtotal: 2+2+2+2=8oz

grand total = 6+30+50+8 = 94oz ~ 6 pounds

Using my forumula this might be good for down to -9F ???
Seems about right, as its been more or less what I've been wearing on walks to work, through some woods and across some ice and through some more woods, but I would really have to test it out for a more prolonged period, at a slower pace.

Its a bit top heavy, but I think that is ok, and some of those top layers are overlapping to the butt area. I'll have to test things out to see where the weak points in my armour. For -20F this weekend I will need to add about 11oz more, so I will swap some stuff in and out from my closet. Don't worry, I won't be testing this too far from home.

http://www.weatheroffice.gc.ca/forecast/city_e.html?nb-23&unit=i

Normal conditions we can and probably should delayer unevenly, but for the extreme for that trip, we should dress more evenly, but still a little more body than legs and arms. In Fall, the extreme might be 20F, and we might be dressed evenly if we got hit with that. In midwinter if we have clothing for -20F, then at 20F, even 0F, we can delayer unevenly, and also risk being more active through the day as we have more clothing to fall back on. Anything below 0F gets very sketchy though, as routine things like going to the bathroom and getting dressed and making water and making meals gets more and more critical, with less and less margin for mishaps. Going through ice is never a good thing, especially with any current, but its not quite the same on a sunny 20F day as it would be on a windy -20F night. Alot of people are so afraid of going through ice they don't prepare for it. Its best prevented by most all means, but if we still go out on the ice, even if its really thick, we should give some thought to going through. That's somewhat of a different topic, but some clothing is better than others for falling in and getting out and getting warm and dry again.