I don't mean to argue in any way, but actually that depends on the incubator. If the incubator is forced air, it should be 99.5 degrees, if the incubator is still air, it should be 101.5 degrees. So it really depends on the incubator as far as optimal tempature. If you set it at 100 degrees with a still air incubator, they would actually hatch late. But it is very true that if the incubator is kept a bit too warm, they will hatch bit early and if it's kept a too cool, they will hatch late. But try to keep it at optimal tempature because otherwise you risk deformaties and such.Usually incubators are set to 99.5 degrees but if you set them to 100.0, some will hatch a day early!![]()