Big gains through late summer, then collapse. But I looked at the charts of 1929 and 1987, and THERE WERE 7-10% SELLOFFS IN MAY before the final rise into late August. So, a 7-10% selloff in the market could start ANY DAY. The selloff for high PE stocks could be 14-20%.
If you look at anything long enough, you can see any patterns you would care to see eventually. I am glad to know that you have been having joy in "finding" patterns in charts. We are all happy for you.