The temperature of forty-degrees Fahrenheit is dangerous for succulent plans. At that temperature, their colors will change and they will develop frost and/or rot. Soaking the plant in the evening soaks the leaves in freezing water for long, and it causes root rot. But no succulents want a lot of water when dormant, nor high humidity at any time of the year. Although many succulents are able to withstand a very brief frost (less then an hour), Agave truncata leaves will suffer damage immediately. Agave ttenuata will look this way after a brief exposure of 32 degrees.