It depends on the eggs you are growing inside the incubator. The most common type grown inside these units is chickens eggs. The optimal temperature for these eggs is between 98-102F (37 to 39C). The crucial thing to note is that you are looking to maintain these conditions throughout the hatching period. It is best if the temperature remains within the specified range. Monitor the temperature regularly and adjust it whenever necessary to ensure each egg has optimal development conditions. As for humidity, it should be from 40-50% during the first 18 days of hatching. From there, you can increase humidity to 65-75%.