Cindy Ord/Getty Images Fundstrat's head of research, Tom Lee, told CNBC on Tuesday that he sees a number of signals indicating the stock market will finish the year strong. Over the last 25 years, the S&P 500 has gained 90% of the time in the holiday season, Lee said. There is also still cash on the sidelines as investors have been cautious about taking risk during the "insanity of 2020." "We've had a surprisingly robust market, I don't see any reason why it's going to reverse in the next two months.