For the uninitiated, September is historically one of the worst months of the year for stocks — and this coming September may face stronger headwinds than in recent years past. CNBC reports on the outlook:

There is also the question of whether the economy will really accelerate, or whether there are cracks showing up in the housing recovery. July's durable goods, down 7.3 percent, also showed a worrisome trend Monday. Much of the stock market's gains this year were based on the view of a second half rebound, and now tracking GDP for this quarter fell to just under 2 percent on the outlook for core capital goods shipments, according to Barclays.