Earlier this year, after the S&P 500 put up one of its best 1Q's of the last 50 years, I posted that in 9 out of 10 years that the S&P had a double digit first quarter, the index closed the year even higher. The only time that it didn't was in 1987 because of the infamous market crash that happened in October of that year.
While the probability is much stronger that a 1987 like event will not occur, if one did it's possible that it would happen in the next 75 days. Historically volatility tends to pick up in late September and October. Below is a list of the 50 largest single day drops in the Dow since 1900. Twenty out of the fifty, or 40%, happened between September 14th and October 29th.