The final three days of June and the first nine days of July are typically very positive for the Nasdaq, and the composite has gained an average 2.3 percent during that period going back to 1985. In that time, it's been negative just seven times. Last year, the Nasdaq rose 1.4 percent in the period.
According to Stock Trader's Almanac Editor-in-Chief Jeff Hirsch, the Dow has been down 22 of the last 25 years in the week after June expiration Friday, for an average loss of 1.1 percent.
The S&P 500, meanwhile, has been higher only once in that week since 2003, but the Nasdaq outperforms, and it has been up 50 percent of the time since 2003.
"A lot of times, there's just straight-up seasonality and recurring market behavior patterns. Greece and other events could easily exacerbate it," said Hirsch. Hirsch said the June quadruple witches, like September's, are particularly negative for stocks.
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Traders have been chatting about the negative seasonal track record and are watching Greece as a possible trigger for selling if its meetings don't go well with euro zone officials Monday.
"That's clearly the danger. If they start a major run on the banks, things could turn ugly very fast," said Art Cashin, director of NYSE floor operations at UBS.
Hirsch notes that June witching is a significant mile marker for the market, as it comes at the end of the first six months of the year. (Hirsch calls this a triple witch though on Wall Street, it's commonly called the quadruple witch.)
Hirsch says every day of the post-expiration week may not be down to make for an overall negative outcome, and the selling could also be short-lived.
"There's more bullish bias towards the very end of the month, and there's still a little bit of June left after next week. The tail of the end of June into July is something we call 'Christmas in July,'" he said.
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