The third Friday of the last month of the first quarter is tomorrow, so look for extra volatility in the market as various stock index futures, stock index options, stock options and single stock futures all expire on the same day.

This is that one day per quarter when all four asset classes expire on the same day, also known as quadruple witching.

Because futures and options investors must close out of their positions on those days, they often witness increased trading volume.

Now you know.