This chart shows the stock market is about to enter a dead zone

Wall Street may be primed for a pullback as the official start of summer gets under way, if history is any guide.

Chris Verrone, a technical analyst at Strategas Research Partners, said in a note Tuesday that stocks are “approaching the more difficult stretch of the calendar.”

Verrone included in his report a chart (which we’ve reprinted with his permission) showing the average performance of the S&P 500 and the Nasdaq-100 index from July to October the last 30 years. A composite shows both typically trade lower during this upcoming period.

Source: Strategas

Equities have been on fire in the first half of the year, with the S&P rising about 9 percent in the period. Stocks have also benefited from an environment where volatility has been unusually low.

But gold and bond prices have also climbed roughly the same amount in the first half, showing investors are still not quite sure about this stock market rally, the analyst said.

“Flows and positioning suggest skepticism remains an operative word in this climate,” Verrone said.

Other technical analysts share Verrone’s concerns.

“Our monthly cycle data continues to support a more cautious technical outlook heading through the Summer into the Fall,” wrote Robert Sluymer, technical analyst with Fundstrat Global Advisors, in a note Tuesday. Sluymer cited peaking global economic data which usually correlates with a pullback in stocks.

He also noted that key technology stocks may have rallied too far, too fast and are due for pullback that could drag down the broader market.

To be sure, Verrone and most of the analysts believes this weak upcoming period won’t be the end of the bull market.

“We can’t rule out a summer pullback / consolidation (the biggest S&P drawdown this year has only been 3.3%), but we’re still more inclined to view weakness opportunistically,” said Verrone. “The calendar is a headwind over the next few months but historically a strong 1H often bodes well for an above average 2H.”