For you in Europe, pay attention to the "transition level" for the Geneva or Milano area, particularly with low QNH and below standard temperatures. It may be darned close to the "granitoculumus" called "the Alps". Same story applies to cross the Andes between Argentina and Chile.
- good advice as always, but I should point out that ATC are required to (and do) adjust minimum allocated Flight Levels to allow for such - that's in Europe, anyway.
I don't think that TL will change with low temps, but you
should never be cleared to an unsafe level (did I say 'never'....?)
and, of course, with QNH on your standby anyway, plus that good old 'situation awareness'......................