Stocks often go downhill after a great summer

David Bianco, Deutsche Bank's chief US equity strategist, forecasts that the next 5% move of the S&P 500 will be down, and that the index could fall by up to 9% before the November elections.

History backs up that call.

In a note on Monday, Bianco pointed out that a big drop in stocks usually happens after the summer if a year-to-date high is reached in July or August.

Since 1961, stocks have dropped an average of 8% in all the sell-offs from the tops in those months to the bottoms before November, Bianco's note showed. Excluding the bear markets in 1987 and 1990, the declines averaged 6.6%.

The S&P 500 on Monday crossed the intraday high it hit on Friday, even as the major indexes traded little changed.

Additionally, Bianco noted that across the year, the S&P 500 has peaked in December most of the time since 1960, as the chart below shows.

But investors shouldn't take this for granted, he cautioned, given the drawdown that has often followed a summer high.

"Chasing summer rallies is risky," Bianco said. "Recently renewed oil weakness and dollar strength challenge healthy EPS growth."

Like any other calendar-based analysis of the market's behavior, this is not a guarantee of what will happen.