At -25 or so the seams in tubes start to fail. You can walk outside and find a flat. You pull out the tube, check the casing, throw in a new tube and try to patch the old one finding six small leaks before you give up, at least the first time. On another note I've thought I've had a slow leak in the rear tire. Squeezed the tire even checked it with a pressure gauge, everythings right. Turns out my ass got soft.