Here in Finland its really cold:-30 to – 40 °C. Is it possible to misure it with PC therm?
(Juha Suuronen) The DS1621 is specified to work down to -55C: I’m not as sure for the other components, especially the 5V regulator. You can either search for the military specification parts (hmmm, sounds hard to find), or use standard parts and checking if it works at such low temperatures (cheap parts have large operating margins), alternatively expose to low temp the DS1621 only.