this isnt UL … but for extremely low temps mountaineers will sometimes use a lamp with a separate battery pack which one can stuff inside ones jacket … keep the batteries warm … most of these lights are also high output
of course many petzl headlamps are "rated" down to -22F …. including my elite and xp2 … as is my rechargeable lithium core for the xp23
as an example of remote pack lamps …
http://www.facebook.com/note.php?note_id=437182694293

Wearing MYO XP BELT headlamps at the fuel pits of Pegasus White Ice Runway, Ross Ice Shelf, Antarctica. PHOTO ©2010 DJ Jennings
Petzl provided a few headlamps to Matt Cherf, a government subcontractor charged with fueling Antarctica's McMurdo Station. He used them in temperatures down to -70 F. He sent Petzl a nice letter recently, and the photo above. Likely most of us will never use our Petzl headlamps in conditions this extreme…but somehow it's nice to know that we could.
"Here is a picture of us at the fuel pits of Pegasus White Ice Runway, a manicured strip of ice that planes land on, on the Ross Ice Shelf, Antarctica. It was taken August 15th, the night of the first flight down here since March, marking the end of the winter season. The two of us were the Fuels Department, in charge of fueling McMurdo Station through the cold, dark Antarctic winter.
The winter was made brighter by our MYO XP BELT head lamps. We used our lamps in temperatures down to -45 F, with wind chills down to -70 F. We began using the head lamps at the end of April until mid August, for that is when the sun left and then returned to us.
The 'belt' battery pack was great, allowing us to keep them close to our cores to keep the batteries warm. The spot/flood feature was also great depending on the job at hand."