Well, i've bowhunted in brutal single digit temps up here in Michigan. It's not the funnest thing to do... haha
I went out and hunted today for 4 hours. Temps in MI were hovering just above freezing whem I went out, with a high of 40F today.
I decided to break out the heavy duty insulated parka and bibs.
I have the Bowhunter Extreme bibs + parka from Cabelas. They're incredibly warm, and have TONS of useful pockets. But unfortunately they're not completely silent. They have some 'dry-plus' fabric that is slightly noisy... but not noisy enough that I wouldn't be comfortable drawing on a beast with them. These are bulky garments, no doubt, but I wore them in my saddle just the same. Actually it was the first time I wore such bulky hunting garments in the saddle. It was totally fine. I practice drawing a couple of times when I got upto hunting height and had no issues with the bulk of the garments.
I have worn these garments down to single digit temps, with brutal wind and snow howling around me and have stayed incredibly toasty. A hand muff is an absolute must, as I have found every pair of 'bowhunting' gloves (ie: with a velcroed wrist for a wrist strap release) to be totally worthless. I have an under armour scent control (zeolite) facemask that I have that works great for cutting wind against exposed areas of the face. It fights very close to skin and you can wear a stocking cap over it. Or I have a scentlok stocking cap if the wind isn't too hellacious. I also have a scentlok ranger-style cap + facemask combo but I have found this garment to be very restrictive for bowhunting. You lose all sense of anchor points (can barely feel knuckle under ear or string touching nose) when using it. It might make a fine rifle season garment....
But I think the most important thing is layering. A good set of baselayers is super important. I purchased a pricey set of ECWCS heavyweight bottoms and top from Bass Pro Shops a few years ago. They are a high-loft hollow core garment that are the warmest winter clothing I have ever owned. I only wear other layers over them sparingly in the house because they are that warm. I will then layer a set of scent-lok lightweight baselayers over those. And if the temperature is very extreme I have a a set of under armour 100% polyester fleece sweat pants + sweater.
For the feet I will wear a pair of merino wool socks, or a thermalite liner sock under the merino wool socks. The lacrosse aeroheads are actually not very breathable boots, so I will often leave them undone until I get to my stand so that my feet aren't sweat rags.
TL;DR My MI Cold Weather Single Digits OutFit
Head:
Under Armour Scent Control Face Mask
Under Armour Scent Control Beanie
Scentlok Fleece Stocking Cap
Baselayers:
Redhead XPS ECWCS XTREME 4.0 Bottoms + Top
Scentlok Lightweight Baselayers
Insulating Layers:
Cabelas Bowhunter Extreme SST Parka + Bibs
Under Armour 100% Polyester Fleece Sweatpants + Crew Sweater
Hands:
Scentlok liner gloves
Cabelas MT050 Handmuff (Extremely warm, but made for dudes with small girly hands)
Feet:
Thermalite Liner Sock
Merino Wool Kneehigh Socks
7mm Lacrosse Aeroheads
Also I like to buy a bunch of grabber warmers in the off season - like march april may. These things are amazing, and they are super useful for all sorts of outdoor activities. I first found out about them for ice fishing, and would use the boot inserts. If it is super cold out I will throw a couple of them into my handmuff, and in extreme cases, attach a couple to my baselayers in rib/abdomen area.
Anyway, that does it. Weather gets pretty gnarly up here in MI. Hope that helps!