3 layers at -16C/3F this morning: (1) thin, long-sleeved merino base layer, (2) medium weight polyester with long collar and (3) wind/waterproof jacket. I'll tuck my balaclava into my mid layer and zip it up over top so that there is continuous coverage, no exposed neck. Even down to -27C/-17F, I'll wear the same things although my arms will be a bit cooler and I will need to get going to warm up. I have a thicker polar fleece mid layer (also with a long collar) which I could use at -25C/-13F or colder but I would likely want to carry my lighter mid layer for the milder ride home.

The long range (14 day) forecast suggests that the coldest I'll experience within this period is -17C/1F so, not really cold enough to test the thicker polar fleece. Now that I've switched boots, my fingers and thumbs are my coldest parts and I don't think that any amount of additional warmth on my arms will really help with that. Next year, I'll have to get bar mitts as I understand they really reduce the cold on the hands.

It's funny how we adapt: here I'm using 2 relatively light insulating layers under an uninsulated wind/waterproof jacket down to as low as -27C/-17F and others talk about 4 layers at 39F/4C. Me, in the fall when it is 4C, I'd still be wearing shorts and short socks with the merino long-sleeved base layer under a long-sleeved, summer weight, cycling jersey, assuming, of course, that it isn't raining. Of course, if there was a foul day in the summer where the temperature dropped from 30C/86F one day to 10C/50F the next, I'd be getting out my winter clothes!!!