Although the US Pacific Northwest has a fairly temperate climate, I distill in ambient outdoors temperature, and have had temperature/distillation interference in 3 distinct aspects of the distillation process, and I suspect these 3 will be the usual culprits for most stillers as the ambient temperature drops.
First, as Bob says, cold can mess with distillation rate by directly cooling the column of a reflux still, or even the riser of a potstill. Low temperature and drafts can make this erratic stilling more pronounced, even stopping a potstill in its tracks while running slowly. As Bob says, insulate!
Second is common and potentially very dangerous freezing of cooling water supply. When cooling water freezes, condensation stops and your still house fills with explosive vapor. Unless you like loud, sudden noises, this is a bad thing. If that cooling water is left in coils or liebigs for long, the copper will be ruined by freezing expansion. Because water is always trying to freeze, this requires constant attention.
Third: This is only a pain in the butt, but if you still with propane, understand the liquid propane boils in the tank to give you the gas to burn, and in boiling removes the heat of vaporization from the system, until the liquid propane cools to the point where your gas output slows way down. Of course, that can stop your stilling. In warmer weather, warm air can supply the heat to boil the propane, but whan it's cold out, you must supply that energy. Pouring boiling water on the tank works. Open flame does, too, but I've seen a high-mountain community burned to the ground by open-flame propane boiling (Snoqualmie Pass, a few years ago?), so I'll stick with the water.
There are probably other things to fuss about when it turns frosty, but these are the 3 I've experienced regularly.
Zymurgy Bob, a simple potstiller Making Fine Spirits
--- In email@example.com, "Ed Barcik" <edbar44@...> wrote:
> Any idea how low of an ambient temperature a distillation can be completed
> successfully? Of course, the column will be insulated. Concerned about low
> outdoor temps.