Since hitting its February low, the has rallied 15 percent and come within 2 percent of its all-time highs. But according to one market watcher, the top could be in for the year, if history is any guide.

Technical analyst John Kosar said that from a seasonal standpoint, Friday marks the end of peak week for stocks in the second quarter.

"Since 1957 we have April being the strongest month of the year for the S&P 500, and on average it has closed 1.5 percent higher on the month since that time," Kosar said Thursday on CNBC's "Futures Now." The S&P 500 is currently up 1.6 percent this month. "That tells me that we've already gone, seasonally, as high as we should," he said.

Read More Expert: Stay cautious in a low rate environment

Kosar also said that the third week in April, which ends Friday, has historically tended to be the strongest week in the second quarter, averaging a return of nearly 1 percent. The S&P 500 was up half of a percent on the week as of Thursday's close.

"Clearly there are some seasonality issues going on right now," Kosar said. "It's telling me to be careful here. … This is a time for investors to tighten stops and watch the markets a little closer than they would normally do."

Perhaps even more concerning, however, is the potential for increased volatility surrounding the June Fed meeting. Kosar said that the last three weeks of June are among the weakest in the fourth quarter, seeing negative returns across the board. And while the Fed is scheduled to meet next week, it's the June meeting that investors are eyeing for the next potential rate hike.

"I'm telling clients not to put any new dollars to work here," he said.