Wall Street is about to enter a historically tough period, and this year it could be even tougher

Once investors come back from Memorial Day weekend, the setup for stocks looks tough. June is historically the worst month for all three of the major averages during midterm election years, according to the Stock Trader's Almanac. The S & P 500 has lost 2.1% on average in the past, while the Dow Jones Industrial Average and Nasdaq Composite have slid 1.9%, each. By comparison, the S & P 500 has gained 0.2% in an average month of June, across all years in data going back to 1950. …