Supposedly, Lithium cells thrive in cold. I don't know about the rechargeables.
And NiCd's generate their own heat in use, but of course you're dealing with
greatly reduced capacity compared to NiMH. The heat is probably why there
is reduced capacity, in fact.
If the light unclips, carry a second one in your pocket and swap them, to
double the runtime. Maybe the second one will then heat back up, and you
can continue the process.
--
Ron Hardin
On the internet, nobody knows you're a jerk.