hello, former lurker here- I rode into work this morning in boston, in the low 20s, since I discovered my truck registration is long expired
ive found a couple of non-electric things that work well in the 20s and 30s. I like to hunt so ive spent years trying to stay warm without electric stuff.
I have several pairs of polypropelene underwear. the thinner blue silky stuff (mines from Wal-Mart, less than 20 bucks I think) makes a great base layer, make sure there's no cotton between you and it. I use that when its above 40,
When its colder, I use the same stuff except that I have a pair of Cabelas "ThermaStat Heavy-Weight". I had almost written the stuff off because if I wear it out walking, I'll melt within 20 minutes. On the bike, I'm perfect.
over that I put a 200 weight polarfleece pullover thing. I got one from "The North Face" as a gift but I looked at their prices and they seemed nuts to me. you can find the no name ones for like 25-30 bucks. I like the pullover since there's no zipper to leak air. the pfleece blocks wind really well and the neck fits tight to keep air from blowing down your neck.
cabelas also sells a polarfleece hood thing that scrunches down into a neck warmer for like 10-12 bucks. i wouldnt go anywhere without that.
With that stuff on, the only problem I've ever had is my hands and feet getting cold. I have grip heaters and hand guards but with plain leather gloves they aren't enough, even wide open. I would say thats going to be your number one problem in a non-electric situation.