From this chart…no rise Jun….Sep and Dec.

Lowest unemployment rate in 10 years means more rate rises…

Why is Sep bad for stocks?

from http://www.investopedia.com/ask/answers/06/septworstmonth.asp:

There are several theories which attempt to explain this phenomenon. One particular theory points to the fact the summer months usually offer light trading volumes on the stock market, as a good deal of investors typically take vacation time and refrain from selling stocks from their portfolio. Once fall begins these investors typically return to work and exit positions they had been planning on selling. When this occurs, the market experiences increased selling pressure, and thus an overall decline.

As well, many mutual funds experience their fiscal year end in September. Mutual fund managers, on average, typically sell losing positions before year end, and this trend is another possible explanation for the market’s poor performance during September.

You need to know the context though…Now it’s not always the case BUT last Sep was actually not bad and we have inflation and fed rate rises this year.  Also SPY has had a great rally this year so far.