The stock market on Monday entered what historically is its worst seasonal stretch of days of the year, according to Bank of America. “September 18 begins the last 10 days of September, which is the worst 10-day period of the year for the [S & P 500] with the index up 40% of the time on an average return of -1.11%,” wrote Stephen Suttmeier, technical research strategist for Bank of America in a note Tuesday. So far the S & P 500 is true to form, down about 0.6% this week. Goldman Sachs noted this week that from now into October is typically volatile because company managements are pressured to give updates on the full year with the third quarter coming to a close. Those early warnings can often be negative. Along with the typical seasonal tendencies, investors this week get a crucial Federal Reserve update Wednesday, with the central bank caught between still-high inflation and a slowing economy. There is also a slew of worker stoppages affecting the economy, higher oil prices and a looming government shutdown troubling investors. The S & P 500 was already in the red for the first part of September and Suttmeier noted that doesn’t make this stretch a buying opportunity. “When the first 10 days or the month are below average, the last 10-days of the month can be challenging as well with the SPX up 41% of the time on an average return of -1.66%,” the note read. Despite what could be a weak period here, the Bank of America technical analyst is still bullish overall as long as any pullback doesn’t break key support levels he’s watching. For example, the market benchmark around 4,425 today is still well above its 200-week moving average of 3,914 so it’s still in a “secularly bullish” trend, according to Suttmeier. — With reporting by Michael Bloom