I've smoked jerky successfully at temps as cold as -15F. Two methods I've used to retain heat in the cook chamber, this was on two different electric smokers.
I had a very nice custom stainless steel smoker I acquired which a friend who is a carpenter built a wood box around it then wrapped the box in 2" foam board insulation. The other was a home built electric smoker I made from a small fridge. I simply wrapped that smoker with a thick old wool blanket ( wool holds up to 70% of its heat value even when wet ).
For each of these I poked a hole in the front of the smoker and pushed a probe style thermometer through the insulation and into the cook chamber to monitor the chamber temp. If you have a wireless therm you wouldn't need to do that.
I'm sure you'll get other ideas from the members here, just relaying what worked for myself. Hope this helps. - Ed
P.S. - This is a blatant cut and paste answer from another thread I just replied to regarding the same basic question. Didn't feel like retyping it all again but the answer is the same. Insulate, block the wind, monitor your temps and keep yourself warm. Rum helps me with that
P.P.S. Attention Moderators...Any chance of a rum drinking pirate emoticon being added to the collection? ha !