There are some 'old timers' have been with adsense for over a year or two. Here are some general trends I found with non-travel releated sites. So far history is repeating, but these things are not anywhere near scientific.
It is based on eCPM but earnings hits a double-whammy because traffic tends to be down too.
June eCPM is stronger than yearly average, then the first days of July sees a step down in eCPM which plummets on July 4. There is a slow recovery on following days for a about a week. Then in mid, July eCPM really takes a hit for the rest of the month. In early August, there is a slow climb back up.
What experiences do other people have in this time frame?