Salesforce Inc (NYSE:CRM) stock is 0.5% higher to trade at $331.52 at last glance, as the cloud software company prepares for its third-quarter earnings report, due out after the close on Tuesday, Dec. 3. While earnings could cause some short-term volatility, there's a seasonality picture taking form that's more worrisome in the long term.

According to Schaeffer's Senior Quantitative Analyst Rocky White's list of the 25 worst returns in December, CRM is the worst performing stock on the S&P 500 Index (SPX) when looking at data from the last 10 years.

Per White's analysis, the security finished the month lower nine times over the last decade, averaging a 4.7% drop and beating sector peers Oracle (ORCL) and Paycom Software (PAYC). A move of similar magnitude would put Salesforce stock near the $315, an area it's traded above since early November.

On the charts, Salesforce stock has been on a tear, finishing 11 of the last 15 weeks higher. This November was the stock's best monthly performance in a year, with help from the 20-day moving average. However, the recent outperformance could have the stock due for a short-term pullback. 

Circling back to earnings, Salesforce stock has a mixed history of next-day sessions, finishing four higher and four lower over the last two years. Regardless of direction, the equity averaged a 7.5% swing the day after reporting, and the options pits are pricing in a slightly larger move of 10.3% this time around.