There are a few things which can cause the humidity in your incubator to go too high. Here a few things you can do to combat it.
If your incubator has manual humidity control without a display, you may find the question below more helpful:
'How do I monitor the humidity in a incubator which does not have a humidity read out/display'?
It is quite common for the humidity to rise too high during the Summer months. The natural humidity level and level of moisture in the air during the Summer can be extremely high in the UK compared to other times of the year - like in Spring - or in other countries. Incubators cannot dehumidify, they cannot remove moisture from inside the incubator. The incubator will not be able to reach a humidity level which is lower than the ambient level which in Summer is naturally extremely high. If you experience this, ensure the incubator is in the coolest room in the house, out of direct sunlight and again, away from rooms which naturally high humidity like kitchens and bathrooms. Some breeders will run an incubator dry during the summer months as it does not need any additional moisture and the ambient humidity level is already at their desired level.