The temperature of your hermit crab's cage should be somewhere between 70 to 85 Farenheit. It's a good idea to get a thermometer for the cage, although it should be fine as long as the temperature in the room is within this range.
Moisture is important for the survival of hermit crabs.
They breathe with modified gills which require moisture and humidity. In a dry environment, the crabs may die from suffocation. You should mist your hermit crab with water from a spray bottle every day to help keep it from drying out. You can also dunk the crab in a lukewarm water bath each week in addition to the daily mistings.