September, meanwhile, is the worst month of average for stocks, with a 0.7% average decline.
Gains would be welcomed by many investors after seeing the S&P 500 Index (.SPX) fall around 16% so far this year.
Still, weighing on the market has been the U.S. Federal Reserve's actions to aggressively tighten interest rates to fight inflation.
The average Santa rally has boosted the S&P 500 by 1.3% since 1969, according to the Stock Trader's Almanac.
The painful double-digit declines in both U.S. stocks and bonds, meanwhile, have made both asset classes more attractive for long-term investors, said Liz Ann Sonders, chief investment strategist at Charles Schwab.