We are entering the summer season for investing, when many professional traders on Wall Street spend summer weekends in the Hamptons.   They also tend to take more vacations than normal (as does most everyone who works).  As a result, it is easier for those traders who are still at their desks to move the market more easily, because trading volume tends to be lighter.  The same holds true for the bots that dominate trading volume, make markets, and move markets.  This brings on more volatility to the market, which can result in bigger ups, and downs.  Friday afternoon, in particular, tends to be particularly light in terms of trading volume.  The higher volatility really does not mean much in terms of actual changes in companies’ prospects.   However, this volatility can rattle investors.