@ Purifier: i shall do my best
They can survive temperatures from about +-2°c if not to long a bit lower to. In nature they can survive temperature far below 0°c but than they are underneath the ground and there it is a bit warmer. Also in nature the ground warms up when the sun is shining. (if you understand what i'm saying

)
Also this depends from species to species. Exotic species are used to a higher temperature so they will not survive low temperatures.