The head winds for stocks are expected to strengthen in September, as a series of major events could make for much stormier markets.

September is historically the worst month for stocks, but this year, the calendar is a minefield for markets. From the Federal Reserve's midmonth meeting to German elections, Japanese tax changes and U.S. budget debates, there's a long list of potential catalysts for pain. Add to that the selloff in emerging markets and rising military tensions with Syria.