The temperature and humidity in an incubator are critical factors in the successful hatching of eggs. The ideal temperature and humidity levels depend on the type of bird being incubated, but generally, the temperature should be maintained between 99°F (37.2°C) and 102°F (38.9°C) and the humidity between 40% and 50% during the first 18 days of incubation.

During the last three days of incubation, the temperature should be reduced slightly to around 97°F (36.1°C) to prepare the eggs for hatching. The humidity should also be increased to around 60-70% during this time to help soften the eggshells and assist in the hatching process.

It is important to monitor the temperature and humidity levels in the incubator regularly to ensure that they remain within the appropriate range. The incubator should also be well-ventilated to prevent the buildup of excess moisture and to ensure that there is a constant supply of fresh air.

Different types of birds may have slightly different temperature and humidity requirements, so it is important to refer to the specific instructions for the type of eggs you are incubating to ensure the best possible hatching results.