Do you remember when old HP product manuals came with "operational limits" notices? I have seen several that stated operating maximum and minimum temperatures, as well as storage temperatures; I seem to recall that there were operating maximum altitude on some of the products as well.
These notices were inherited from the time where HP was the world's best measuring instrument producer - and you needed to know if the measure had been taken within the right operating bracket - but that's not the case anymore.
At least you can make tests for yourself. The HP15c LE works well at -5ºC (23 ºF), at 3.571 m (11.716 ft) of altitude, on Jungfraujoch Sphinx observatory:
The view from Jungfraujoch, in mid-Switzerland, is amazing - you see miles and miles of glaziers, and several 4k+ peaks. You can see as well possible falls of more than 2000 m when you stop with the train in the north face of the Eiger peak - since 1935, at least 64 climbers have died trying to climb it. No wonder I took the picture firmly grabbing the calculator!