Wifezilla is right you will need to know where you are at when it comes to humidity and temp.
I'm sure more folks can chime in on this but since you do not have a thermostat you might need a heat sink of some sort.
Possibly a sealed jar of water or something like that. Search the forum on "heat sinks"
I wish I knew more on the topic but I'm sure there are folks on the forum that know a lot more on this topic.