Volatility and wild market swings have become commonplace during the past several weeks. But if we take a look at the markets for the entire month of May, the picture looks mighty gray.

In what best can be described as an extremely melancholy month for the market, May saw the Dow drop 7.92%, and the S&P 500 sink 8.2%. The NASDAQ Composite was the worst of the three major indices in May, plunging 8.29%.

As you can see by the charts below of our “four horsemen” -- the S&P 500, the 30-Year Treasury yield, the U.S. Dollar Index and the iShares FTSE/Xinhua China 25 -- it’s been a very busy, and very volatile, month for all.

The big news with the S&P 500 is that it descended below its long-term, 200-day moving average (red line). This breakdown in the S&P 500 -- along with other factors that comprise the Fabian Plan -- prompted my Successful Investing advisory service to issue a sell signal in domestic equity funds.

There was a flight to quality in Treasury bonds due to all of the turmoil in the equity markets and in Europe, and that caused Treasury bond yields to plunge, as can be seen here by the chart of TYX.

The flight to quality continued in the U.S. dollar, as the greenback gained significant ground on rival foreign currencies in May. When the euro is shaky, you want your capital to be in dollars, and that’s precisely where investors headed last month.

Finally, China’s woes continue, as seen here by the index that measures the nation’s top 25 Shanghai listed equities. Here, too, we see the extreme volatility in Chinese stocks since the beginning of the year.

So, will the May gray turn into June gloom for equities? Will we see a reversal of fortune in Treasury bonds and in China? I hesitate to make a prediction here on the fate of the four horsemen; however, one prediction I think I definitely can make with confidence is that there will be a lot of volatility on whatever path this market decides to take -- so please, please, please, whatever you do, be very careful.