Yesterday, we highlighted the 25 best S&P 500 stocks to own in August in the last 10 years. Today, we're going in the other direction, looking at the 25 worst S&P 500 stocks to own in August. A quick scan of the list reveals one theme; a prevalence of oil and gas producers. Among the seven oil-and-gas names on the 25-stock list are, blue-chips Exxon Mobil Corporation (NYSE:XOM) and Chevron Corporation (NYSE:CVX).

According to data from Schaeffer's Senior Quantitative Analyst Rocky White, over the last 10 years, XOM averages a drop of 3.5% in August, with only two of the 10 returns positive. Last seen trading at $44.45, the $44 level -- which has stymied Exxon Mobil stock in the last month or so -- could continue to serve as a stiff ceiling as summer winds down. Year-to-date the security has taken a 38% haircut.

Looking at Chevron, White's data shows that the stock's average loss for August comes in at 3.2%, with 20% of the returns positive. CVX was last seen trading at $86.94, down 28% in 2020.

Lastly, both Dow names sport attractively priced premiums at the moment. XOM and CVX's Schaeffer's Volatility Indexes (SVI) of 35%, respectively, both sit lower than the bottom 20th percentile of readings from the past year.