Start of 3rd quarter: A weaker period for stocks?

Measure expectations for second half: Pro
Measure expectations for second half: Pro   

As traders watch developments on Greece, they are also teeing up next week for the start of the third quarter, often a weaker time for stocks.

So far, the S&P 500 is up 1.7 percent for the quarter-to-date, and it has historically averaged a 0.6 percent gain for the third quarter going back to World War II, according to S&P/Capital IQ chief equity strategist Sam Stovall.

But in the third year of a presidential term, it often does better, gaining 1 percent.

Read MoreConsumer spending rises most in nearly six years

The third quarter is also seasonally the time when stocks can be choppy. "History says when approaching the third quarter, fasten your safety belt. It's going to be a bumpy ride," Stovall said.

In the third quarter, six of the 10 key S&P sectors have averaged losses since 1989. Defensives—consumer staples, health care and utilities—have outperformed, as has energy, he said.

Traders work on the floor of the New York Stock Exchange.
Lucas Jackson | Reuters
Traders work on the floor of the New York Stock Exchange.

The S&P 500 is down very slightly—0.2 percent—for the month of June so far. The S&P has been higher in July 54 percent of the time. It has averaged a 0.9 percent gain in July, going back to World War II, compared to a 0.7 percent gain for all 12 months, Stovall said.

Read More US weekly jobless claims total 271,000 vs 272,000 estimate

The S&P 500 fell 6 points to 2102 Thursday, as markets continued to await a resolution in the Greek debt talks.

"We're coming back to that line we need to hold, or else everyone is going to be talking correction again. It's 2,090/2,095," said Scott Redler of T3Live.com. "2,106 was breached today, and that's when we had a quick move lower. That was basically pivot support.

Read More The state skills gap: Who's got talent?

Redler said the market is sending mixed messages with the Dow Transports at 2015 lows, but the biotechs and Russell 2000 breaking out to new highs.

"You have the end of the quarter Tuesday, and you have another deadline for Greece. It should be interesting as the market heads to another inflection point. We've had this a lot, where we could start a correction or break out to highs," Redler said.

Read MoreGold falls for 5th straight day, traders await news on Greece

What to watch

10 a.m.: Consumer sentiment

Finish Line reports earnings before the bell.

Read MoreUS services sector growth slows in June: Markit

12:45 p.m.: Kansas City Fed President Esther George speaks on the payments system.

1 p.m.: Baker Hughes rig count on number of active drilling rigs in the U.S. and Canada

Read More America's Top States for Business 2015