I find it amusing that I can tell if it's getting below -5F (approx. -21C) because after that temperature the colder it gets the warmer the indoor, alkaline battery operated thermometer at work goes up. So currently it's -20F (approx. -29C which is the D.Dog's favorite all around temperature to lounge around outside in) and the indoor thermometer reads 68F (20C)! Which it's clearly not because I daren't even take my long underwear off indoors and I refuse to even cross the parking lot without my hat. So instead I peer out in the dark at the bi-metallic sensor which currently is accurate. But sadly, this thermometer, like all I've ever seen commercially available, stops at -60F (approx. -51C). Which is clearly not good enough here because we bury the needle at least once a winter. Mercury is no good either - it freezes at -39C (-38.15F), where both Fahrenheit and Celsius are almost the equal.
Perhaps it's time to get an alcohol thermometer - do you think I can make my own? It has a suitably low freezing point ( -113C , approx. -171F) - the weather gods have mercy on us if we ever get to that limit!