In addition there is not a single place in the universe that is that cold. Jool analogue Jupiter is about -90 and even Pluto only gets down to -250. the background temperature of intergalactic space is -271
Gotta take frequent breaks when working on Laythe, since the atmospheric pressure is only 80% that of kerbin and oxygen levels must be lower.
And I guess kerbals are pretty acclimated to cold temperatures, since it never gets beyond 20°C on Kerbin. Still, it must be chilly on Laythe, with maximum temperatures of 6°C. Again, the game is in developement and theses values may change anyway.