While actively growing, conos (like many succulents) need warm days and cool nights. Low temps around 10 C and highs around 25 C are probably ideal, although the plants can easily withstand near freezing conditions for a time. It is worth noting that seeds germinate best if kept at about room temperature, and will not come up at all if they're kept too cool. During the summer, it is best to protect dormant conos from excessive heat.