During the winter months, the plants will still be growing; the new bodies will be increasing in size as the old outer leaves begin to shrivel. No water at all should be given during the winter … the soil should remain bone dry no matter how shrivelled the plants become. The new body actually draws out the water stored in the old leaves to continue growth, so do not remove the shriveled leaves. Lithops should not be exposed to temperature lower than 40°F (5°C). If the plant are too near a window during freezing weather, they will be damaged by frost even though the room seems warm, so move them back a little during really cold winter weather.