As we enter August, the S&P 500 Index has seen a three-month winning streak, with a 14% gain. However, historical data shows that August is typically a bearish month, with an average return of only 0.17% and a median return of 0.54%. September is even worse historically, making this a challenging time for investors.

Looking at two-month timeframes, August through September has averaged a loss of 0.73%, with 54% of returns being positive. The lack of significant upside when positive and large downside when negative contribute to this poor performance. Positive returns average 3.52%, while negative returns average a loss of 5.71%.

When the S&P 500 has seen gains in the three months leading up to August, historical data shows a positive trend for August and September. In the 12 instances since 1975, August has been positive every time, with an average gain of 2.83%. The following two months also saw positive returns in 11 out of 12 instances, averaging a return of 3.06%.

Stocks that have performed well historically from July to September include Nvidia (NVDA), which has reached a market capitalization of $4 trillion. On the other hand, some stocks have consistently performed poorly during this time frame over the past 10 years.

Read more at Yahoo Finance: Can the S&P 500 Rally Overcome Bearish Seasonality?