My eggs are on day 13 in a styrofoam, air circulated incubator. The air sacs seemed too small, based on images and drawings so I began running dry three days ago. The temperature has been a constant 99 F, within a degree. I do not have a hygrometer. My concern is that the air sacs do not seem to be getting any bigger. Development of chicks appears to be normal. I live on the coast of California. The humidity is around 75% but today got up to 90% as it was heavily misting, almost raining. What can I do to decrease the humidity inside the incubator so air sacs with become larger?