I've been broadcasting and following trends on the internet for over 16 years. Internet radio give us the ability to track audience listening trends better than terrestrial radio. My findings are that internet radio listening during the Summer drop during the months of June, July and August. Why? you may ask. The answer is quite obvious. Since many people listen to the radio while at work, many of those people take vacations during this time dropping the radio listening audience quite a bit during this time. This is the trend for US base stations.
Usually the audience takes a slow climb after Labor day as everyone is back at work, the kids are back at school and everything returns to a more normal flow. The next and more severe drop is after Thanksgiving. If you are a Christmas music station, you will see an increase in listeners during this time. Other stations will experience a drop. There is competition from the Christmas only stations and again people are busy, take vacations from work, school and routine things.
Don't despair, the audience will return in January and many times steady growth results between January and June.