The best temperature to incubate eggs generally depends on the species, but for most common poultry eggs, such as chicken eggs, the ideal incubation temperature is around 99.5°F (37.5°C) when using a forced-air incubator. If using a still-air incubator, the temperature should be about 101°F (38.3°C) at the top of the eggs, as temperature can vary within the incubator.
It's important to maintain a consistent temperature throughout the incubation period, which usually lasts about 21 days for chicken eggs. Additionally, humidity levels should also be monitored to ensure successful hatching.